Her ex is a woman

I knew from the very start of our relationship that my wife was involved with another woman before me. She said she has always been bisexual and I accepted that. She said she was over being with other women and that it was always more of an emotional rather than a physical thing with girls. She also said that she never had more than one lover at a time and I believed her.
We went out for dinner and her ex was there with another woman. My wife introduced us and it was a bit awkward when she suggested we all eat dinner together but I agreed. There I was with my wife and two lesbians, I really felt left out even though they all were very nice to me. As they talked I started to realize that my wife knew this other woman a lot better than I thought. We ate and I went to the restroom, when I came back they acted like I had interrupted something but I didn’t ask. Shortly after that we said our goodbye’s and headed home. On the ride I asked what did you guys talk about when I was in the men’s room?
She didn’t give me a straight answer so I dropped it. That night she was a lot more affectionate than usual, it didn’t sink in until the next morning. Being with those two women got my wife turned on!
When she woke up we sat around and had coffee as usual and I asked her about her ex and that other woman, I asked how well did you know that other woman? She became very uncomfortable and tried to avoid my question but I said honey I love you and you can tell me anything. We have always been very open about our prior lives.
She said while she was dating her ex that woman sometimes joined them in bed. She looked at me waiting for my reaction. I knew to be careful to not act all turned on thinking about her having sex with other women even though she knew like most men it really did turn me on. She couldn’t see under the table but I was sitting there with an erection that was just throbbing. Then I said something I should not have said. I asked was being with those two women why you were so horny last night?
She just stared at me and I knew I had fucked up. She got up and went into the bedroom without saying a word. I waited trying to figure out what to say to her. A few minutes later, after my erection went away, I got up to apologize to her. I went into the bedroom and she was sitting on the bed crying. I sat next to her waiting for her to go off on me. Instead she just turned to me and said she was sorry and that she missed having a woman in her life. She said she was completely happy with me and she didn’t want to ever lose me but lately she has been craving the touch of another woman.
I couldn’t help it but I got erect again this time I couldn’t hide it. She looked down and saw it, I expected her to get pissed off but instead she said it was OK, she understood and then she lifted her robe and got on top of me letting me inside of her. We went at it and while I was still inside of her I whispered if she needed another woman in her life I would understand but she had to always be honest with me.
We both finished in a way we had not finished in a long time. Later that day she got dressed and said she would be back later. She told me nothing was going to happen, she just wanted to talk to her ex. Hours later she came home and told me things had gotten out of hand and she had sex with her ex.
I know I have to get over my insecurities and allow her to be who she is. I also know that my fantasy of a threesome will never happen as her ex is not at all interested in men. But maybe someday some other woman?