She ignores me so I ignore her and she breaks up with me And says she never meant anything to me but she means the world to me I don’t understand
One of the best lessons to learn in a relationship is that you aren't a mindreader, and neither is your partner. Don't assume that your partner automatically knows what you want and how you feel, rarely this is the case. That's why frequent and clear communication is so important.
In your situation, it sounds like she isn't getting the attention she wants from you. She ignores the relationship (so that you'll notice) and she'll say things she may not fully believe (I never meant anything to you!). You, on the other hand, are thankful she's in your life and don't understand why she's acting like this. The wires are crossed somewhere and it's good you're taking time to assess.
Spend a couple hours to ponder the ways she's added to your life, made you a better person, and tell her those things without fearing you'll look vulnerable. Make her feel appreciated. Then, invite her to talk openly about whatever's on her mind. Ask her what her ideal relationship would look like, one where she feels fully appreciated. How would things be different? Then see if you can incorporate her responses into how you interact with her on a daily basis. Maybe some of the drama will go away if both of you feel like you're being truly heard.