re: My fiancee cheated on me.

That absolutely sucks, but you should be ecstatic that you found this out before you got married and you should be in a lawyers office this morning already drafting a custody agreement.

I know you don't want to think about this but trust me:
frick that bitch, when it comes to family court you cannot be nice. Call a lawyer immediately and begin custody proceedings. Never concede and DO NOT tell her you did it.

Save all text messages and emails and go download an automatic call recorder and save all her phone calls and voice mails

Lastly, do not become petty or jealous or angry. The best revenge is a life well lived. Keep your head high and don't let her upset you. She'll get off on it. Be cordial and polite. Treat her like a nice stranger. Don't ever shite talk her to your daughter.

Nothing will ruin your ex's life more than you staying respectful, being the bigger man, and completely moving on with your life. She'll get no vindication or justification and she'll just rot.