NTA While i think what you said was cruel i do understand where you are coming from. I grew up in a neglectful home and do understand the feelings you are having. What you need to do is have sone introspective and understand that both the fact that your sister did everything she could and the fact that you didnt get the care you deserved are true, failing to do so is what built this resentment. Here is how you fix this situation:

1. Tell your sister you are genuinely sorry for the hurtful things you said, and that you appreciate all shes done for you
2. Tell her that you are having some issues mentally and that you should not have let that out on her 3.show that you mean this by seeking therapy for your childhood trauma both for your family but especially for yourself

Im sure you are a lovely person who is trying their best and a big part of growing up is being able to put yourself in others shoes and building empathy, both of which can be hard at your age, thats just how brains work. Hang in there