Dave, CalTechGirl, and Christina, thank you for your most helpful comments about my situation. You have no idea how helpful they were. Thank you, also, to those who sent me email on the matter.
Christina, honestly, I think your situation was worse. If anyone ever suggested to me that Prince Charming might not be the father, I'm pretty sure I'd find the inner strength to beat back my politeness and rip their head off, leaving nothing but a bloody pulp in my wake. I would turn them into fresh chum. In particular, saying these things at the bedside are outrageous. So, I think you win.
Although, CalTechGirl's situation sounds like the equally awful flip side of the same situation. Sort of the less evil doppelganger, or something.
All of your comments were helpful, for now I know that I am not alone. The stereotype exists for a reason. My family would never say the equivalent of these things to Prince Charming. They know that I would rip them a new gastrointestinal system if they did. Of course, they are also polite enough not to voice their nastiness (should they have any) in a public forum to the person in question. They genuinely like Prince Charming though, so I doubt they have any similar feelings about him as she has about me.
It seems universal that I should have a serious chat with Prince Charming about how these comments make me feel. He doesn't have a lot of control over her or her mouth, but it would go a long way toward explaining to him why I prefer his uncle and aunt over his mother. It might also make him a bit more understanding about why I'm not so eager to visit. Not that he's particularly eager, himself.
So, I will talk to him about it. He can't change it anymore than I can, but refreshing his awareness might help me feel better.
I have thought about it quite a lot and am still uncertain about what to do about her, however. I am still loathe to leave her comments stand unchallenged, but I shall see how Prince Charming feels. If I would prefer that I do my best to let it slide, I will try to do so. My only concern is that the comments seem to be getting less veiled and more insulting all the time. If he prefers that I bite my tongue, it will be with the caveat that if her insults grow overwhelmingly burdensome, I may react without thinking at some point in the future.
But I will discuss it with him.
Thank you all again. I really appreciate your kind words and encouragement. At the very least, it is nice to know that I am not without a sense of humor (however warped).
This whole thing has brought out another resolution. I am not going to be that kind of mother in law EVER. As long as my child is happy, I will be content.
So, I will try to be polite and have better manners than some exhibit, but grace only goes so far and I have a mean temper.