My friend doesn't care, or remembers anything?

my friend never remembers anything i do, yesterday i had a college interview, today not a word of it, but some people who i hardly speak to was like how did it go yesterday. Its not just once its every time i do something, like an exam or i have one next and they dont, they either dont care and tell me to shut up, or just dont listen. But they do something its the news of the day, and i ask them how it went, if i go to doctors, not a word, they go omg thats all they talk about. Today she was like, which just makes me feel whats the point, she said 'ive come to an age in my life (she is 15 so she sounds stupid) where i dont care about anybody but myself', i felt like wtf, shall i go and kill myself then or ur family see if you care then, but it felt directed at me. my other friend who copies everything she says was like yeah me to but tbf if she said i stuck a broom up my bum she would go yeah me to. I dont know what to do, she goes in a strange mood like every week,1 day a week she is happy, i know im happy all the time and think of others, sometimes to much but she takes the piss tbf, should i walk away, talk to them , play the same game. comment also if u have had/got friends like that.