You r daughter is 22 years old; she is an adult. I know how much you don't want to hear this, but it's her choice now. There's a person on TV I very much admire--Ellen Degeneres. She's gay, and she seems like a very good person. I think she might be older than her mate.
Not everyone is heterosexual. This might not be such a bad thing. Please keep an open mind: please don't assume that your beautiful baby is being taken advantage of and sent down a perverted road by and older and more experienced person who is preying on her innocence. That might just not be the case.