what do i do?

One of my best friends is graduating. I am in a tight best friends group of three people, my childhood best friend who is going to be a junior, the oldest of the group who is going away to college and then there is me who is going to be a sophomore. i'm going to call the best friend going to college AC and the other one LT. well we all three want to make this summer amazing and live life to the fullest before we are separated for months. But recently AC has been ignoring LT and I and we are really worried because she is drifting away and just slipping away and me and LT don't know what to do... we have asked her and she said she has been busy and that she is completely fine... we know her inside and out and we know her family and she isn't doing enough chores or anything during quarantine to be ignoring us 24/7 and IDK what to do, Sometimes she is happy when she is about to see us because she has too but sometimes she just wont talk and she suggested that she was just in the way and that she didnt want to ruin our summer.... i really miss AC and i wanna have fun but idk how to tell her that any different from what i have already told her.... LT and i have both told her straight up everything. But.. anyway...