Something about the outfit Christina had on has been bugging me. To me it looks like a daytime outfit, a little bit "Annie Hall"(dating myself here)... for a young woman to be wearing. Especially with the hat.
It's rare to see anyone wearing a large brimmed hat in a club. IMO, and from what I have seen, for a night of clubbing, it's little black dress or quality jeans with a sexy top, and heels kind of thing. Aren't those the 'uniform' for clubbing and going out?
The woman walking in the parkade could be anyone.
If I had a well thought out plan to disappear from my life, I'd probably choose something just like that.. you can't see her body shape at all. people would assume it were me. She sounds like a very smart young woman, maybe it's something she planned.
Why she would disappear on purpose is anyone's guess...how was the clothing business going? Was there a huge loan due and payable?
A group of concerned friends trying to save Christina from abuse/addiction/ some bad people?
Or as someone else suggested, an accidental overdose and everyone she was with was scared to report it?