Most Helpful Girl
Sorry dude, this person is a yandere, I have dealt once with this type. The good point of this could be that she is not a good close friend neither of one of your family members nor of your friend circle so the next thing can help you even though it is going to be very cruel and rough.
Give her the cold shoulder. Change your mobile phone or tell to the people with whom you are leaving with that if she calls, that you don't want to talk to her, and that they should tell her that, tell her to get lost instead of making excuses for you.
Don't feel guilty and don't let anyone else to make you feel that way (even if there is a party in her favor outside of your house with candles and songs pleading to return with her), just think that she has looked for it, to be treated like trash. In the end you won't be the villain, because you have tried to reason with her first, but she guided you to treat her like that.
Most Helpful Guy
Just ignore her and one of two things will happen. She will either eventually get tired of it when she finds someone else to harass, OR, she'll start getting crazier and blowing up your phone and coming by your apartment like she did with the cake. When THAT happens, then you'll have enough evidence to warrant a restraining order or other action.
Save ALL texts from her, save call logs of every time she's tried to call, and if she starts coming by your place start documenting the day and time.