I figured things were good. I cant imagine her thinking this new lifestyle will be better for our daughter.
It's not a "lifestyle" it's a sexual orientation. And I think the answers are different depending on whether she's bisexual or lesbian.
If she's really truly bisexual - this is an affair no different than if it was a guy and proceed as you would in that case. I'm sorry you have a small child. If she's not willing to give up the affair and go to counseling I would proceed with a separation so she can experience the full effect of her affair and what life would be like without you. If she's ashamed of her affair and willing to work on the marriage then you can.
On the other hand - my guess is she's really a lesbian. She's probably just now coming to grips with the truth of her sexual orientation and that's not likely to change. The fact that SHE talked you into a threesome with another woman is proof that this was on her radar years ago. In this case it has nothing to do with you or anything you did or didn't do, it's just a fact of life. It's too bad she grew up in a time or place or religious culture where she wasn't able to deal with her sexual orientation earlier in life rather than creating this mess but some people still need a lot of time to come out of the closet. If this is the case, let go, have a peaceful divorce, and try to coparent as best you can with her. Don't take it personally because it's not about you, and it's a GOOD thing to find out now so that you can move forward with your life and find a partner who takes as much joy in sex with you and you do with them.
