You can't un-ring a bell. There is a book you should read -- sorry I can't remember the name of it (perhaps someone here can help) but the basic premise is that when your partner is past the point of no-return you shouldn't chase them. That is the completely wrong thing to do. At this point, all you can do is give them the space they want and start making serious, epiphany-level changes. Then hope she sees the changes and her emotions soften towards you once the edge of her disappointment and weariness wanes a bit.
This process takes weeks to months, btw. Not days or a few weeks. If you expect a hurrah for your efforts, you are doomed before you start. Make changes for your own reasons, not to win her back. Good luck.
Second thoughts can generally be amended with judicious action; injudicious actions can seldom be recovered with second thoughts.
--Cyteen by C.J.Cherryh