My girlfriend acts like a child and its so unattractive

Hi,
I actually have a lot of experience with research concerning child-like behaviour in relationships and relationships in general. being a woman myself having studied phychology, I think I can help you out.

1) why everyone's talking about "daddy issues"? there is a huge misconception about this topic and basically 'daddy issues' is referring to the fetish whereby the female lacks a father figure and uses their partner as a substitute.
You do not have to have 'daddy issues' to have a 'daddy fetish'; there are a lot of girls who have this fetish due to the fact they like the 'Dom/Sub fetish' (which the majority of women like, it's in our genes) whereby the male is always dominant to the female during sex. this may have branched off and created this new 'daddy fetish' in your girlfriend which then creeped into everyday to day lifestyles with you and her.
This may or may not be the case with your girlfriend but is a VERY common cause.

However she may just want to be cute because she wants to be presented or expressed that way to you now.
or she's grown more comfortable with expressing her true-self and now she's showing it to you.
or another reason, which I think MAY be the underlying cause, rather than the "daddy fetish", leading me to..

2) identity crisis
when someone can't define who they are because they have been told otherwise or they have been triggered someday which leads to an alter in their persona. this may have happened to your girlfriend whereby when you told her you love your sister a lot more she was 'triggered' by this as a result, causing her to act more like a child to solve that problem where she thinks you don't love her enough.

my conclusion, what I think you should do, and questions to ask to further help you:
As I said before, I think she's going through an identity crisis, I have had my own experience with this where I had trouble understanding who I was and changed my persona to fit what I thought was best to impress. this is the same situation with your girlfriends where she's having trouble understanding why you don't love her enough and that's why she's changed her persona to fit what you think is an 'ideal girlfriend'; to match your preferences basically.
I think you should text her after exams (good time to tell her) and tell her you've noticed her change over the 3 months. now, when you put a woman through a situation like this by texting her all this, she will inevitably be sad of course but to solve this you have to understand women don't want you to make the situation better by attempting to change her perception, they want you to solve it! to solve it, you gotta say this in short: • say you've noticed the change • tell her you love her a lot still but you don't want this to ruin it all • tell her you don't know if this is to do with the fact you said your sister was better, but family love and relationship love is completely different and just because you love your sister unconditionally, it doesn't mean you don't love her more than anything and would do anything to prevent breaking up (you may not believe this but this will sure get to her heart) • DONT tell her you don't like the whole child-like persona, tell her you feel "a little uncomfortable" and you just miss the way she was before • don't make it sound like she can't change her ways. compliment her, tell her "I know you're a strong woman that has an incredibly bright personality and a stunning appearance, you always are, so why the change? " the "are" is incredibly important because it implies she still is the person you love and her old-self is still down there somewhere and she can easily return. additional emoticons "" are really useful because it gives a visual portray of how you're feeling and I know that sounds really unprofessional and obvious but people underestimate their effect on others, it differs an sad person from a blank person who doesn't care.
• tell her you have concerns for her health because you truly care and love her and she needs to eat properly as its noticeable and worrying to you.
affection is incredibly important because you don't want to ever sound like this situation can't be solved. overwhelming love is always the key to a future long duration relationship together in the hard-times.
questions:
does she act cute with you in bed? this may be evidence to the fact she likes daddy fetishes if not an identity crisis
how old is she? identity crises are most commonly in people aged 11-20

She acts like a five year old, presumably because she thinks its cute and ill like it. But I really dont, it makes me feel like a pedo and a babysitter and its soo uncomfortable. Even worse, shes losing a lot weight and starting to actually look like a kid and honestly I am very unattracted to her now.

sad thing is, it's not like this is how she is and I have to "accept" her or leave, we've been together a year now and shes started this new persona like 3 months ago and I just dealt with it. So really shes the one thats changed, Im guessing it's because shes more comfortable because we've been together a while.

She used to be so womanly and have such a powerful presence - which is why I went crazy for her in the first place and pursued her. And even now with other people she's confident and womanly but to me she acts like a five year old.

she basically puts on a child like voice and like mumbles and says random stuff and goes 'oooh im so sorry im weird teheheheehe' and you should get the picture by now. I just find it so fake and weird and I already have a baby sister I dont need another weird kid in my life right now.

I just feel like screaming to her 'stop it its not cute' But I have no idea how to communicate that to her without her getting upset offended and self concious.

please please can somebody help me, this is ruining what was once an amazing relationship. I still love her but shes really pushing me away.

She acts like a five year old, presumably because she thinks its cute and ill like it. But I really dont, it makes me feel like a pedo and a babysitter and its soo uncomfortable. Even worse, shes losing a lot weight and starting to actually look like a kid and honestly I am very unattracted to her now.

sad thing is, it's not like this is how she is and I have to "accept" her or leave, we've been together a year now and shes started this new persona like 3 months ago and I just dealt with it. So really shes the one thats changed, Im guessing it's because shes more comfortable because we've been together a while.

She used to be so womanly and have such a powerful presence - which is why I went crazy for her in the first place and pursued her. And even now with other people she's confident and womanly but to me she acts like a five year old.

she basically puts on a child like voice and like mumbles and says random stuff and goes 'oooh im so sorry im weird teheheheehe' and you should get the picture by now. I just find it so fake and weird and I already have a baby sister I dont need another weird kid in my life right now.

I just feel like screaming to her 'stop it its not cute' But I have no idea how to communicate that to her without her getting upset offended and self concious.

please please can somebody help me, this is ruining what was once an amazing relationship. I still love her but shes really pushing me away.

I agree with what you've said, but I wouldn't call these fetishes. Dom/sub dynamics within relationships are more of a lifestyle choice, rather than a fetish, and the "daddy fetish" which you refer to implies that his girlfriend is attracted to literal fathers, rather than (possibly) father figures, which plays more on the dominance and submission. I believe that the dd/lg dynamic fits more into what you are saying here...maybe. But that's just me being picky

I agree with what you've said, but I wouldn't call these fetishes. Dom/sub dynamics within relationships are more of a lifestyle choice, rather than a fetish, and the "daddy fetish" which you refer to implies that his girlfriend is attracted to literal fathers, rather than (possibly) father figures, which plays more on the dominance and submission. I believe that the dd/lg dynamic fits more into what you are saying here...maybe. But that's just me being picky

Agreed. Though I doubt the OP really wants to hear that instead of telling her to stop it, he should tell her to find someone who likes it. Which is what I think he should do.

I totally agree with you, I struggled to find the right word to suit it and lifestyle fits perfectly!