I sort of had something like this, being a male.
When my wife and I "opened" our relationship, it was because without talking, the limits of our relationship had come to a head. I thought, at the time, that SHE thought I'd slept with someone else and was telling me "This is okay".
Later, I find that her impressions were different and valid and good, and there was no cheating involved, but we opened it in my brains because she though I already had.
So when she ended up, rather quickly, with 3 partners and I had NONE except the one person I was falling in love with but not seeing on a daily basis, I felt a bit of envy. Also, I felt a bit of "How the hell do you have so much energy!?!?!?!"
I've got to agree here with GroundedSpirit that compersion matters! I have been envious, but I've never actually been jealous. I sort of let my feelings towards my wife ground me. She could do 50 guys in a train but she still loves me for the memories and values we share and nothing around that will shake us. That said, those memories and values don't have her driving home the next morning with a MASSIVE smile on her face.
Finding her explore herself and her values doesn't by any means take away from who we are and what we want mutually.
The flip side to that is that, with me, most of my relationships seem to be non-sexual but extremely intimate with sexual tension. The whole "getting laid" thing has shifted in my eyes from the goal to a form of that sharing. I don't know what your sex drive is like but with me, I find that I'm exploring the forms of relationship I want, more than the onjes that have the highest chance of me getting laid and still liking the person in the morning. My own priorities have shifted because of my experience.
Connection is the path to passion. Passion is not the path to connection.