You said she made you feel as if it was YOUR fault??? Of course, lol. That's how they deny guilt and don't fess up to what they've done. They know they're wrong when they say that shit.
Listen, if you want to see if this chick is truly sorry and really...really really really wants to be with you then there's only one thing that must be done. This will also show her your no schmoe. Tell her you want the same thing. Tell her you must get a threesome with her and some other chick, but x2. That's right, TWICE, with two different chicks, two different occasions. If she does not agree to this, then dump her, she's not sorry. Eye for an eye when it comes to this type of shit my friend. Don't ever forget, we may be men, but you must be better than that. Be a Wolf among sheep.
If you really want to be with this chick, do what I said above. Show her there will be consequences for fucking you over. You don't have to beat her or whip her ass or anything like that. But, she must know, in the future, if she decides to stay, if she does wrong, she will suffer consequences. Two threesomes, with two different girls is a good consequence to start.
Now, after that, dont' ever bring up the cheating again. If she thinks this is drowning you in misery, she'll stomp all over your balls again. Show it doesn't mean shit to you because you can leave anytime and replace her. Trust me, that's what she thinks of you. Flip the tables on her. Show her your love and emotions is not to be fucked with.
Now worst case scenario. If she doesn't agree to it, walk away. Yeah, it will be the hardest thing you've ever had to do. It will make you wallow in your on misery for a few weeks, but this my friend is GOOD. It will make you stronger the next time around and make you choose better or at least know how to handle women better in the future. You must never become bitter. Become stronger. There's to many women out there that WANT you to show them YOUR boss. If they start thinking THEY'RE boss, you've lost. So if you have to dump this chick, just sweet out the pain. But the worst thing of all that can happen, is you do NOTHING. If nothing is done, and you stay, your asking to dip your dick in sloppy seconds all the time while she lives off of you. That my friend is the truth. Women are master manipulators. You've got to be a master manipulator yourself if you ever want to win at this game. I'm sorry, that's the way it is.