I did I just don't see how someone can Chang their mind in a day

It's rarely over a day.. It's at least over a few days or weeks.

Just means she was lying to me then cause like I said she flipped on me in a day

I see three possibilities: 1. She didn't know if she wanted to do this or not/ didn't have the courage for a while, but decided to now. 2. She didn't want to break your heart so she did this, thinking it'd be easier than if she directly called it off. 3. She somehow did suddenly have a change of heart in a day. It may be none of the above though as it's just a guess.

It's probably one of those I just want closure that's all