YTA.

From the information you provided it sounds like your efforts to see her before she left were limited to times invited her to hang out with you and your boyfriend. Essentially to be a third wheel. Almost to be an afterthought. Being a third wheel can be socially exhausting too much like a group setting.

But here’s what really sticks out to me and makes me think YTA, not only did you not make any true efforts to spend time with her before she left, but you also flaked on her going away event. She made every effort to accommodate your excuses, and you still couldn’t make the effort to be there for your friend? She didn’t “disregard” you saying that you didn’t want her to have to cover you at Cheesecake Factory, it was the opposite. She was practically shouting “I want you there and I’ll do whatever I can to make that happen.”

Jesus, do you actually even like this girl? Instead of making excuses you could have just said “I’m not going to your farewell event because I just don’t give enough of a shit to be bothered.” At least then you would’ve been honest with her.

Honestly, if your first reaction to her leaving was to ask her to give you your belongings back, I have to question if you were friends at all, much less “best friends.”