She was probably hurt not to be invited to your party, and is lashing out at you. Considering she's 4 yrs older than you, she's not being very mature about it. But some people are like that when they get hurt.

You should explain to her gently that yr mom didn't want you inviting more than a certain number of people to your party and that- due to the age difference- yr mom didn't want you to invite her for some reason.

Tell her yr sorry if she's hurt; you like her and want to continue the friendship. If she doesn't accept yr apology& continues to act weird and distant, it's time to forger her friendship and move on. You might be better off with friends yr own age- though the problem might be her personality rather than her age.

Give it a last try and if she won't let it go, let HER go.