Can he trust her now?
D is my primary partner. He has a secondary partner, C, as well. He has also been interested in R for a while.
The relevant history is as follows. D was ready to date R about nine months ago and I fully supported it. We are all poly. They did hang out a few times and made out but stopped short of any genital contact. R said she wanted to take things slowly and D is not a pushy guy at all. Then, R pulled back, just about halted spending actual in-person time with D, but continued to have an email and phone relationship with him. She told D that her reasons for pulling back from actually spending time with him face to face were the fact that she was not yet over a breakup with her female primary partner, and also, the fact that she wanted to have another female primary partner before she added a male one. Basically, "I don't want to date a guy at all until I'm in a serious relationship with a woman."
R went forth and dated quite a lot of women, from the sound of it. I felt bad for D because he continued to ask for in-person time with her, even as just a friend, and got a lot of "I'm too busy this week" responses, while she simultaneously vented to him about her bad dates and lack of connection with this woman and that woman. I started to suspect that R was really gay, not bi, and in denial about it, because she continued telling D what a wonderful connection she had with him, while choosing to spend her time with people who sounded much less rewarding to her. I encouraged D to move on, find someone who really wanted to be with him. This person materialized a few months ago in the shape of C.
A few weeks ago, D and I had a party and invited both R and C. R had met C once before, but this was the first time she saw her together with D. As R was leaving the party, she told D, right in front of me and C, that she had time to see him an evening that week if he wanted to.
After the party, I told D that I thought that R clearly was only interested in him again because she saw that he'd moved on, with C. D disagreed with me and went off to spend an evening with R. And wouldn't you know it, R wanted to finally be sexual with D that night. D told her that he wasn't ready for full-on sex (and I don't think he had condoms with him anyway), and they stopped short of intercourse and oral sex, but there was some manual sexual contact for the first time. At the end of the evening, R also disclosed a sexual partner, of some duration, whom she had never mentioned to D before. The partner is male.
D has since told R that he is honoring an agreement he and I made a while back, to pursue only one outside sexual relationship at a time. Their status is platonic friends. D wants much more from her though in the future, and R says she does too.
I am starting to feel that R is not to be trusted, because she did not disclose a sexual partner until after D had told her that sex was off the table, and it sounds like she might not have disclosed him at all if D had agreed to have sex with her that night. I also think that R was dishonest with D in telling him that she only wanted to date women, in pursuit of a female primary partner, when that was clearly not the case.
Should I tell D that I don't think he can trust R, based on these two things? It doesn't matter at present, since they are just friends for now, but I know D wants that to change. I'm open to renegotiating our agreement and having that change too. I just don't feel good about R right now.