My sister is very mean, very selfish

Hi All,

I have a sister is who is same age as me.

she has lost me two phones when I was 15, 16 (never even bothered to get it back or find the phones), this June I left the phone in her car which I asked her to retrieve which she put in her wardrobe (which I seen) and somehow she's lost it and did not even bother to give it me back, I lost all of my contacts. Even now I asked her where's the phone? She knew where is was, were she put it.

From ages 16-23 she never once said hello to me, smiled and spoke to me is a very disrespectful manner. I remember at a wedding, I came back from talking to my friend and went to sit by her, looked at her and with a mean face she said "whattttttttttt?" very rudely all the people around started smirking at me, she knew this was socially unacceptable way to behave.

I had a university essay to hand in last minute next day 12noon deadline in may 2015 and this was 11pm where my laptop messed up and I asked her if I could use her laptop which she did, however, because I had to download programs and she gave me the user account, a password popped up, I asked her can you type in the password please or give me and she can change it later, which she said no all the time even though this was the most important assignment in my life since my university year was ending, and I was on the verge of crying. I had to ask my cousin to lend is laptop 11pm in the night, went over to his house and slept their!

Before I got another loan yesterday, I needed a guarantor for a loan (which she will not pay anything anyway) and she said twice she'll do it later (never did) and then she declined even though she knew it was very important and I said please a lot. She did not have to pay one penny.

I do everything in the house (cleaning, cooking, even contributing towards the bills) and she said aggressively yesterday "you don't do anything(she swore), whatever, you do nothing".

I helped her decorate her room two weeks ago, shifted everything, drop her off at the shopping centre all the time, went to my aunties one hour earlier to accommodate her (because she had to go to the gym later) these are some of the things I do for her.

She's been very mean lately, ignoring things which I very important, not bothering to help at all and saying things out of sheer arrogance.

I don't know why she does that.