Chewbacca
^MiLs, like grandparents, cannot dictate what younger family members do.^
So where do you draw the line at rude, bad mannered and discourteous behaviour by a guest in your home Gagajo? Do you just continually turn a blind eye to their rudeness and pretend that you don't mind it, just so that you don't offend them, for fear that you will be sidelined? Aren't good manners, courtesy and being polite reciprocal? Surely, when you visited your MIL you had basic good manners didn't you? 
I did initially Chewbacca, but my MiL was a controlling, unpleasant woman. So after I'd been married to her son for a while, I'd avoid her every chance I got. And yes, at times I would just slip away. I once even volunteered to work over the Thanksgiving holiday (American family) to avoid spending it with her.
The only similar situation I've been in was with my daughter's partner. He behaved much as the OP says her DiL behaves and yes, I totally ignored it. Frankly, I preferred it when he avoided me. Less awkward that way. But because I didn't want to alienate my daughter, I tolerated him.