Update to Sister In Law, posted by Anonymous.
Here's the update: my MIL passed away the day after I wrote this
(which also happened to be my 31st birthday). After giving my BIL the
silent treatment the entire six hour drive, my SIL spent the rest of
the weekend doing the same to my husband and I. And she's yet to even
acknowledge the existence of our six month old son.
When it came time to travel across the country for her funeral, she
refused to come because she said she needed the right to completely go
off and blow up at anyone who even "looks at me funny, even if it's in
the middle of the funeral" and that she expected him to back her up
100% of she did it. He said he couldn't do that, so she refused to
even make the trip. To be honest, it made the weekend less stressful
for everyone there.
Now, it's looking increasingly likely that she won't be my SIL for
much longer. She has been lying to my BIL about a variety of things,
blowing up at him every other second for nothing and everything, and
when he asked her to come to counseling to try to work out their
issues, she said she'd go, but she really wasn't interested in putting
much work into the relationship. So..while I'm sad that my BIL is
having to go through this (he's an awesome guy), and so soon after his
mother's death, I'm actually kind of excited about the possibility of
being able to hang out with him, spend time with him, and do family
stuff with him with out having to worry about her.
Just writing that letter made me feel much better.