Should I be worried about my boyfriend and this girl?

Hi guys.

So me and my boyfriend are living together, we have known each other for over 1 year now. There's this girl that is friend of both of us as well. She already has a boyfriend. Her boyfriend actually my boyfriend's best friend. But he's working overseas at the moment.

Yesterday me and my bf had an argument on why I told "everything" about him to this girl. I actually didn't. She was one of my good friends before, I did tell her things about my life but when I realised she wasn't a nice friend to hang around, I've stopped talking and texting with her actually. My boyfriend said he was pissed about me saying everything about him and our relationship to this girl. He kept asking how much does she know about him. I asked him whats the matter, why would he care if she knew something about us. He said its weird when he talks to her, she just knows everything about his life in min! We actually have had this argument twice now. I don't get why he is caring so much about she thinks. Then I asked him again, if I told this to another person, would he also care like this? He said no, it's because this girl is our common friend and he talks to her, meets her a lot so that's why it bothers him..???

I actually apologised and admitted that was my fault. I should haven't told her anything about us. The problem is that she asked, and I just simply answered. But I was wrong so I said sorry to him. It seems to me like he cares SO MUCH about this problem than anything else. That's why I'm not sure if I'm crazy or not. If there's something going on, he always asks about her ( even though he can ask about our other friends ), he cares about she knows and thinks about him/our relationship based on our arguments, he actually told me to not be mean to her ( he knows I hate her ). He always brings her in our conversation ( even tho he knows I hate her once again ).

Furthermore, from her side, I've been noticing her behaviour towards my bf for awhile now. She always asking about him, about our relationship, about our sex life. There was one time when we were just texting, when I mentioned about him, she immediately called me to ask more about him! When she first came to our place, she asked my boyfriend what he thought about me and my style, his thoughts about living with me, if we had that "connection" to talk all day or how we spent time together... the list goes on and on. I actually didn't answer anything because I thought it was weird so I just let it slide through. She has been snitching a lot about my life to my boyfriend as well and yesterday he confronted me about a lot of things that I told her before. That's why I've stopped hanging out with her.

Am I crazy? Is this normal? Or should I be worried? Hope you guys can discuss and help me out of this situation. I haven't been able to focus on anything because of this problem.

Thank you! Have a good day.