So this could be more succinct but it's 3 am and wont be. I like my metamour quite a bit from our emailing/meetings together, and she says she likes me, but because of the circumstances, it seems like she and I will never be great friends, hang out, etc.
We've met a couple of times, I'd like a happy poly family sorta thing where I hang out with my husband's, and my boyfriends partners (including his wife, the metamour in questions) but she just is not into that I would like my husband to want to be good friends with my bf, cause I think they'd like each other if they spent the time to make the effort but he just isn't into it
The point is, what I want, and what others want, aren't always going to be the same. I am not going to avoid social situations where we would both be there. If I/my husband are invited somewhere, and she is, I will go if I want. No reason at all for you to not go where you want, you have not indicated any reason why you aren't wanted, and it just seems that you want to withdraw because she doesn't want to be your BFF - I imagine if she wasn't married to your boyfriend, you wouldn't care about her opinion enough to worry about if you should or shouldn't go to a party/club/etc.
So, maybe you will, maybe you wont, all live in a communal house someday. I wouldn't put so much focus on that at all now, it's early days. (I also have an ex husband who has spent the last 20 years following pipe dreams about "grand plans" which have only now finally started panning out, and it left an ugly taste in my mouth for all the times grand schemes ended up going nowhere, so I second the idea that perhaps she just has heard her husband talk about all sorts of wild ideas that aren't necessarily going to be around in another 6 months ) Why SHOULD his wife want to be your best friend? Why don't you just focus on your lovely relationship with your boyfriend?
No I am not just siding with Anne because of my username, but really, I (as a 39 yo person) probably wouldn't invest too much energy in my partner's relationships if I don't have a ton in COMMON with them. I don't take it personally when they don't want to hang out with me more than occasionally (and yes, they tend to like me, his partners just have busy lives and other shit to do, and I've found OSO's partners area also fulfilled and not sitting around hoping for company) but I think it's great when there is a reason for a friendship.
I just want to say, over-reading into it and trying to distance yourself from events, or to "punish" her for just not being "that into you" by avoiding her is not a useful tactic for anybody. I am sure she thinks you are perfectly nice (or her husband would know it) but just doesn't want to spend her limited free time hanging out with you if she could be doing something more fulfilling or enjoyable. Don't take it personally, just because you are nice doesn't mean your metamour wants to spend hours talking to you about anything. As others have said, if she isn't hostile, interrupting your dates, or out to get you, consider yourself blessed. The older we get, the more we realize life is finite and that no minute should be wasted doing anything we don't want to wholeheartedly do.
Happiness will never come to those who fail to appreciate what they already have.