EDIT: Skip to my second post for more precision.
TLDR: I have FWB with ex girlfriend. FWB's long distance boyfriend is told we are fucking, and asks her to choose. Do you try to keep FWB, and if so what do you do?
I started seeing this girl (Diane) back in March. We had both come out of serious LTRs recently, and definitely were each other's rebounds and quickly became good FWBs. In May, she suggested an open relationship (mainly because we were 3 hours apart) but after about a month of this she broke up with me. We didn't talk all summer really, then she came back to college where I was and we quickly became FWBs again. Coincidentally, right after we broke up her ex-LTR (Jack) wrote a long apology letter to her and they started "talking" again. In her eyes, he is "the one", but they haven't gone back to anything official yet. When Diane and I started seeing each other, Jack had just bought a house halfway across the country, and now he's trying to convince her to move out there with him.
So keeping our FWB on the down-low (It would definitely piss him off if he knew we were fucking), we've managed things pretty well. We go shopping together, cook together, she cleans my apartment, we give each other massages and of course have (some really good) sex. This has been a great arrangement for me, since I basically get all the perks of having a girlfriend without having one - great for concentrating on school and pursuing other women. It also helps keep me from getting one-itis with anyone else, and I don't have any other potential FWB's on caliber with this one right now.
This wasn't a problem until last night. Someone told Jack that Diane and I were fucking... it's been passed off as a fabrication, but this made Jack tell her last night "me or him". Today, we went shopping together again and she did some cleaning, and we talked about things a bit.
She hasn't made her decision verbal, but the fact that she's hanging out with me when "she's not supposed to" should be a good indicator that she hasn't chosen him yet. She's told me that before she came back to school, she "promised herself" that she wouldn't hang out with me or sleep with me. Oops
If you could defeat a woman with logic, it'd be simple. One of the reasons Diane and I started talking was about how toxic her relationship with Jack was. All of her friends and family express disgust over him, and even Jack's family wants to keep them apart. I know better than to do that though, I actually straw man him if anything. Right now, he can meet her emotional needs but I am (quite content with being) the "other guy" she can hang out with and sexually please her. I wouldn't say I'm in love with her, or want her back, but we certainly have feelings for each other. Its not the BEST sex I've ever had, but it definitely something very important to me. She's quite attractive (HB8-9) and the more we fuck, the more I learn about being better at sex. She's into quite a bit of kinky shit, and makes me a better lover. I wonder if my FWB with Diane ties me up emotionally/physically from other girls and setting me up for disaster when/if she gets back together with Jack... but otherwise I see no reason not to continue doing this as long as possible.
The question of course, is what is the best way to go about this? When Jack comes up in conversation, do I "straw man" him or just avoid talking about it? Should I give her a semi "freeze out" and let her figure things out? What does it sound like SHE wants?
For the record, I am seeing a couple other women (but not at fclose) and I have some emergency fat sluts I could fuck at any time.