So my GF hates her friend whom i am now good friends with because the girl is better friends with me/?

Ok so to paint the picture of this story you need to know it from the start promise it won't be too long. Ok so me and my girlfriend met at University we were both in our first year this year and have been together for 7 months now. Ok so i met her around two weeks after the start of uni when i met her she immediately introduced me to her friends all of who she had jus met in the two weeks of uni before she had met me. Throughout the whole year me my girlfriend and her friends all went on nights out together there was one other guy with us when we went out so it wasn't just a chick fest. Anyway so as i am seeing her friends regularly and going out with her and her friends i become friends with her friends. I become good friends with one of her friends in particular because we have mutual friends. All of my girlfriends friends however did the same course so slowly she began to lose touch with them as they all saw eachother much more regularly than she saw them. Bare in mind we still went on nights out clubbing with them but my gf and her friends just weren't close friends more like casual friends now. Anyway the friend of hers that i have mutual friends with me and her chat regularly on messanger we don't call eachother or even meet up just texting really and she's real easy to talk to and friendly so its all cool. Now my gf has suddenly become extremely jealous, she said she thinks the her friend Amy whom i've been talking to regularly is a b*tch for trying to befriend and get close to me and leaving her out of our friendship. BUT my girlfriend isn't really the social type she waits for people to contact her and if they don't they drift a part with me if i generally like someone as a friend i don't mind giving them the odd call or text jus to see how there doing even if they don't necessarly call me to me its not a big deal. Anyway so as she is not social she barely talks to Amy and as i am i talk to Amy alot and as we have mutual friends aswell we gradually just become better friends than her and my gf. Now my gf seems to think the girl is up to silently hate the girl (silently because the girl doesnt know) the girl even texted her the other day and she just ignored the message and was like why would i want to talk to her and that she hates that ugly b*tch. Now as shes my friend it doesnt sit right with me for my girl to be insulting her behind her back especially when there is no need to aswell. It's pretty ridiculous that she has such an extreme reaction to such a small thing, she said she doesn't think the girl likes me but thinks the girl is a b*tch for befriending me and talking to me more than to her but i'm telling her that it's not even like that because she barely makes an effort to be friends with the girl and me and the girl have mutual friends so obviously were going to become better friends than her and the girl but she seems to think that there is a way a girl should act around her friends Boyfriend and the girl is acting inappropriately by befriending me which i get but because we all hung out as a group and went clubbing together for year i'd think i became a friend and part of the group to everyone than just her friends boyfriend. I dunno what do you think?