I’m in an open relationship and I have two partners- my boyfriend also has a girlfriend as well as me, and while I’m okay with his girlfriend I just don’t particularly like her. Like as a person. I can stand being around her for small amounts of time, but I don’t think I could ever consider her a friend. I worry that, if my boyfriend ever asked for me to hang out with her, that when I say no he’ll get upset. I just want him to understand that, and I don’t want to offend him.
A healthy relationship includes the freedom to be honest, even about unpleasant or inconvenient truths. Both of my partners have friends that I don’t particularly like, and we make it work. The conversation usually goes like this:
“I don’t really like your friend Blevin.”
“That’s fair. I won’t invite him to things you host and won’t be annoyed if you make yourself scarce when he’s around.”
The trick is not to be accusatory about the friend or metamour - don’t say or imply that they’re a bad person, or that your partner is blind to some critical flaw, or wrong for liking them. Just let it stand as a personal preference of yours. I hate jazz and metal music (I know, musically my palate is Unrefined), so when my partner goes to jazz or metal concerts, he finds someone else to go with. Not everything, or everyone, must be mutually enjoyed.
So if your boyfriend suggests that you become one-on-one friends with his girlfriend, it’s okay to politely decline. “I’m happy to be nice to Stephanda when you have her around, but she’s not someone I’m interested in hanging out with more.”
If your boyfriend wants to know why, try to take a shrugging but gentle tone. “She and I just don’t click. I know she makes you happy, and I love that you two have a good relationship, but I’d rather just let her stay on the edges of my life as your partner.”
If he can’t handle this honesty, if he gets angry or defensive or demands that you give her another chance, that reaction is his problem and inappropriate on his part, and you’ll need to think about whether you can be in a polyamorous arrangement with someone whose terms of the relationship include “you are not allowed to dislike my other partners ever” - but I wouldn’t worry about this unless it actually happens. Give him a chance to be healthy and accepting of this imperfect and inconvenient, but not really problematic, situation.