Walk away from her and don't look back. You already let her back in numerous times so she thinks she can get away with doing that.Simple.

I know you'll find it "impossible" to just wallk away but it'd be better for you in the long run, either that or tell her she makes up her mind today, else she's lost you...

She has what? hours to think about this,how much time does someone need?

Time is a great healer...