Here is my POV in case it helps you.
The issue at hand is that G feels the need to share details of our time together with M, in order to make him "get used to it".
I think you have a problem with G. SHE might have a problem with M, but the one crossing
your line is G when she tells co-owned data without your consent. After all, she could choose to "make him get used to" her keeping her privacy and her saying "No" when he gets overly nosy instead.
I wonder if she tries to say no and then he acts out at her so she capitulates. "You
have to tell me... so I can get used to it! How can I get used to it if you don't tell me anything?!"
Like "poor lil ol me" stuff?
Not that it matters. He is HER problem, not yours. You could focus on your problem : her behaviors affecting you.
INFO OWNERSHIP
I think there is a difference between "need to know" and "want to know." Sex health labs for hygiene could be shared freely. I think that's a NEED to know so people can give full informed consent when they tango with others -- it shows their sex partner is clean, and keeping up with health and hygiene matters.
Details of when, and how, and what sex acts were performed -- that's a WANT to know/WANT to share to me. It's not necessary to know for hygiene or health reasons. Some people like hearing/sharing details like that and some do not. You seem to want to keep those private. You could say NO to G.
When you and G share sex, the people present are you and G. That means any information about that instance is co-owned by you and G. If she's telling other people things about it without your consent? That is crossing your information management boundaries. She's crossing a line.
Your current agreement seems to be "You can tell him things until the end of his 6 weeks of counseling." Which is reasonable enough. When the 6 weeks are up? That's it. You close the door. I think you could make it clear to G that you no longer give her consent to share info with M without your consent past that deadline. Make the new agreement.
Getting all up in you and G's biz forever is inappropriate. Ultimately it is not your penis going into her vagina that trips him out. It is what he THINKS about it that trips him out. The one who changes his mind is him, so he has to work on his thoughts, core beliefs, etc with the counselor. He could try to exercise some self control over his wonky thinking if it causes him discomfort. Learn to talk himself down when he's getting cranked up.
Rather than try to manage where her vagina goes or where your penis go so he doesn't think or feel anything yucky at all.
G HAVING BOUNDARIES HERSELF
He messages her constantly when we're together, he freaks out if anything we do deviates from whatever plan he has in his mind of how our time should be spent.
So he acts out his fears. He also tries to control happenings because he feels a loss of control when he experiences yucky thoughts or feelings.
But who is the one answering the phone tantrum while on a date with you? G. So you have a problem with
G's behavior right now. She does not say "No." She does not let it go to voice mail.
To me it sounds like he pulls the string and she goes running. You could talk to her about this.
She has stated that if she doesn't tell him, "it will make him feel like it's a secret."
That's right. (Sex acts you and G choose to engage in) are a private matter between you and G. What is so horrible about that? G and M themselves will have their
own things that are private -- cute jokes, how they like to share sex, and whatever else. Not the end of the world.
If M has a need to be included or be reassured, she could do it in ways that do not involve crossing the line with you. As a hinge she has agreements to keep with BOTH partners. If one partner asks her to do something that betrays an agreement with the other partner it is ON HER to say "No. I am not willing to do that. I'm sorry. Could I help you in a different way?" It's on the partners not to be putting the hinge in the middle like that. It is not kind.
I think it is enough for M to know you two are lovers with safer sex practices in place at the end of the 6 weeks. It's enough for M to know he can ask for sex health labs and they will be freely given. He does NOT need to know details of every lovemaking session.
You have made allowances for transition time. 6 weeks is up when the 6 weeks are up. No more "peeks into the bedroom" after that without your consent. If M wants to know something private between you and G, he has to understand he needs BOTH G and your consent on that info.
Which means you could ask G to stop sharing information you both co-own without your consent. You consent to sex health labs, but details of lovemaking are off limits. Then sit back and see if she can respect your boundary or not. G could learn to set limits with love. Get her relationship with M on healthier ground -- esp if either one has gotten enmeshed or codependent.
Does G feel responsible for managing M's feelings for him? Is she not willing to let M learn how to manage his feelings appropriately on his own with the help of counselor? Does she need counseling herself?
Galagirl