First of all, I personally feel that your girlfriend is a relatively straightforward and cheerful person. In Northeastern dialect, she is "self-acquainted." It doesn't mean anything, this kind of character is very popular. You feel uncomfortable because you and she are different in terms of making friends (especially general friends). You are not used to her close-buddy approach, and at the same time, she does partially ignore your existence.

You can have a chat with her. Now that you have a boyfriend, you should be careful when interacting with other members of the opposite sex, not to let others misunderstand, and to reassure your boyfriend.

It can be seen that you still love her very much, and you only care about these things if you love her. hehe. Wish you happiness.