You've got enough reason to dump her.
Don't even be specific at this point. She's not being honest with you, you don't owe her an explanation. If she runs to you asking for a reason (she will), just say "you know the reason". See what pings. Its called 'giving them enough rope to hang'.
If she acts relieved or like she doesn't care, that's an answer too.
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