No, you can't stop her from doing what she's hell-bent on doing, but you damned sure don't have to make it any easier on her, either. I don't think you should have allowed the two friends to stay in your house (hell, YOU should be in your house!!!). Why don't you want her to be alone? This woman NEEDS to be alone, to think about what she's doing. Any introspection that she might have done is out the window as she's out galavanting with these two now.
I think you just allowed it to be the "nice guy" again.
Do NOT pay for any of her schooling, unless ordered to by a judge. So long as she is emotionally invested in your marriage as your wife, you are committed to helping her fund her dreams. Once she checked out of the marriage and began cheating on you, that "contract" went out the window with the soiled bedsheets.
Do you want to hear things about OM from her? Personally I think it's incredibly disrespectful, and I would never allow it.