I can see your frustration... but (LOL), I'm going to take the other side just for a second...
She's married, and she and her husband met you, who was sexual and together with both of them. Then she got pregnant. Not only that, but she has a high-risk pregnancy, which means not only is she limited in what she can do, but she is most likely seriously anxious and scared about the health of her baby.
So she's anxious, worried, stressed and filled with pregnancy hormones (which, just to explain, make you a bit extra crazy and sensitive anyway), she's not getting the sexual side of her met AT ALL, she's probably feeling huge and uncomfortable and miserable.
And because she's pregnant, now it's not ALL of you, but just you and him. So the unicorn situation has become you and him instead-- an issue that can be problematic when it happens even without all of the extra added stress and hormones involved.
So she's miserable, hormonal, stressed, scared, and not getting her sexual needs met.
I'm kind of understanding why she may feel like she's losing her connections, you're getting them, everybody else is having fun and she's in hell.
An exaggeration, I know... but pregnancy is tough even without beginning poly relationships and fearing for your future child's life.
I do agree with maybe speaking with him, or her and him, and expressing your concerns with how you feel you're being treated. But you may want to consider that while you are upset that she is not taking your needs into consideration, you really aren't taking her situation and needs into consideration either.
And communication with a pregnant woman can be difficult at best-- ask any husband who'se gone through it with their SO's. Picture the worst crazy PMS you've ever had, and multiply that times 10 and go through it for 9 months.
Expecting her to be entirely rational and communicate clearly right now (at least all of the time) is probably an exercise in futility.