Reading your post, a couple things popped into my head.
The first - or maybe most important, is that it may be that you and her really are not connecting especially well. You probably care about each other etc but the real depth is just not there. That's ok - as long as you don't EXPECT otherwise. It's entirely possible for a successful 3 way relationship - even in triad form - to exist even though all combinations are connecting at different levels. In fact, I think all people connect at different levels, so to expect equality may be unreasonable.
I'd say just accept where it is today and look for opportunities to grow the bond deeper when they appear. It may be that she's sensing the same thing (discomfort when all 3 together) and is trying to avoid it ?
Now..........that being said..........
The interaction, decision making, discussions etc that seem to leave you on the sideline............that's something that takes time to change. AND everyone has to WANT it to change and so be able to discuss it openly but gently. You say they have been together for 10 yrs. In that length of time you get set into certain styles and routines that you usually aren't even aware of ! Now, everyone just has to realize that old format has changed and all need to be open and ready to modify some of the old patterns. It may not be as much an unwillingness as much as it is an awareness of the importance. Like you said yourself - they seem to fall back into old, pre-established patterns. Sometimes just a gentle "whoo hoo - I'm here too !" is enough to get the point across.
It needs to be addressed - but not harped on - if that makes sense. If you don't see any honest effort and improvement after a few months you may have to evaluate the sustainability of these particular individuals. Or just let it drift into a "V".
Good luck - try to be patient. Old habits die hard they say.