meko, I am glad you started this thread because I am a bit confused about your relationship with B.
You consider yourselves a triad? 3 equal partners, all primaries? Or you're in a love/sexual relationship with BG and are merely friends/metamours with B, a V configuration?
If you're in love and sexual with BG, but just trying to be friends with B because she is lovers with BG, many people find it isn't necessary to be just as close with the one you are in love with, as it is to be loving or even friendly with her lover. There is certainly no need to have 3way sex if you're not attracted to her.
Especially now, you're apart from BG. There really is no reason to be best buds with B if you are quite different people and disagree on many issues in life. Sure, it's important to be civil and polite, but there doesn't need to be an intensity of love and caring if you're not feeling it. You certainly don't need to force the issue.
Love withers under constraint; its very essence is liberty. It is compatible neither with envy, jealousy or fear. It is there most pure, perfect and unlimited when its votaries live in confidence, equality and unreserve. -- Shelley
Mags (poly, F, 61) loving miss pixi (poly, F, 39) since January 2009, living together since 2013
"Master," (mono, 34), miss pixi's Dom for 3 years