My wife has a lesbian lover.

Arrange an MFF threesome. Bang the girlfriend while she does your wife. If you like it, accept your new situation.

It is not strange at all that you are not hurt at all but are intrigued. Or should I say that it turns you on? Every normal straight man has phantasies about women having sex together. So why not make the best out of it. Just let him have sex in front of you and just watch and enjoy.

If your wife says she want to stay with you, you are the one to know best if she is honest. Some many men are happily married and would never think of leaving their families, but like to have sex with another woman.

Throw the rug munching bitch out the door. Find a live in. Sue the cheating cunt for child support and live happily ever after. Hey, I did just that when the same thing happened to me. So I know.

Is it normal? No, but everything is relative.
It sounds like your wife is polyamorous, which means she feels love for multiple people. That being said it's still cheating and you have every right to leave her, and any evidence of this outside relationship will help you in court; but this isn't a mandatory reaction. If you still love your wife, are open to this idea, and they are both willing to be open and honest with you then go for it. I would NOT suggest letting your kids in on what's going on though. Non-traditional relationships are normal these days, but there is a difference between "I have two loving fathers who are faithful to each other" and "Mommy cheated on daddy and he accepted it". Monogamy is a fragile thing to begin with, and having a third wheel involved in your kid's life could rip the kids minds and your relationship appart.
I'm not a psychologist, but that's my perspective. Either way you go be careful and document evidence in your favor; because if your wife went off the tracks lile this behind your back, it's going to be hard to trust her from this point on.

My dude you can totally get a guilt threesome out of the deal unless you only want your wife and if that's the case much respect for you.

If you're still into this relationship, there's nothing wrong with having this continue. I would, however talk as a group about your feelings, as well as discussing how important openness and honesty is for you all.

Tell your wife you will only agree to her coming over if she and your wife get it on in front of you! When they all nice and sloppy, whip your dick out and fuck them both.

This will make them both jealous and your problem will be solved!

It's a trap

Sounds like you have a Ross Geller problem.

We need proof!