Lying

Alexis
So my girlfriend and I have been on rough terms lately and she knew that I couldn't handle much more hurt or pain.
Also I told her that lying and cheating would be the two things that would truly make me break up with her.
Well she lied to me again about going to practice this last week. She says she's been going to look at spots to have us take pictures and for her to propose to me properly but I don't know  what to do. 
Do I give her another chance after already saying it was her last or do I truly end it this time?
Anyone been in this sort of situation before?