My sister (22f) told me she hates me (20m). She didn't give any reason.

I'm really lost and I need to vent.<br><br>My sister and I used to have a great relationship. We have a 17 year age gap so we were basically best friends.<br><br>It started to go south after my grandpa died. We were sitting at a restaurant and she said "I hate you" and walked away.<br><br>We haven't been close since and we barely even talk.<br><br>We are sitting at home and she says out of nowhere "I hate you".<br><br>I ask her "why?" She doesn't say anything and just walks away.<br><br>I don't know what to do.