You don't have any choice, but you still need to be a father to your D. You are an equal part of her life. If friend is putting up 80%, what is he getting out of the deal? If she's only paying 20%, that is not an investment. Her friend will have the investment.
It sounded like you were willing to put in money. If she feels she can't afford to put a roof over your daughter's head, would you be willing to help provide that? Owning a house isn't the only option.
I'm just saying - you're a parent and have a stake in your D's best interest too. It sounds like the two of you might need to do a little less walking on eggshells and a little more discussing the specifics of how this will realistically work for the benefit of D.
It'll be painful, because that discussion will have to take place under the auspices of "We're D'ed" rather than "I want you back," but deal with the business first and the trust will follow. It's already begun, right?
lodo
PS - glad you're still exercising. Helps to take out aggression, calm the mind, keep yourself in shape, etc. I just started doing bikram yoga - sweat like crazy but boy do you leave feeling great!