Interesting how some people react isn't it? I'm glad your wife has been a rock for you, and understand how hard it is when, inspite of your best efforts, you can't maintain a good relationship with another member of the family.
FWIW: I have a friend that is very very close, who blew off the initial news (she is also in the medical field), saying when she saw the MRI screenshots she was glad to see it wasn't very big nor likely to be a problem.... several weeks after my surgery, she was asking me if I recalled how concerned she was when she realized that I had a BIG tumor and it was already pressing on places - not good, freaked out! Hmmm, I just don't know why people aren't honest when they hear serious medical news, but I find it difficult to deal with. We're still friends, I wouldn't quit caring about the friend that let my son throw up on her antique rug 20 years ago so I could have an anniversary evening out with my husband, but she lost some of my trust and respect - and like your MIL, had caused some inconvenience and upset for me post-op which just piles on the wondering why?
On the other hand, I had a friend that I only met a little over a year ago, show up at the hospital as I was checking in 6:30 am, and kept my husband company the whole 14 hours of surgery. She cleared her calendar to be my driver the week after I was released, and if I got tired, would just look at me and say sweetly "Chris is sinking, I'm taking her home." There must be a special place in heaven for such a special lady.
I've had some people be complete arses, yet I've had the best support from unexpected directions. I'm relieved that my manager at work is one of the good ones, and blessed that my Son has been intuitively there for me. I had similar experiences 35 years ago when I had surgery to reconstruct my hip as I had giant cell tumors - I guess these things bring out the best and worst in people.
Keep noticing the bright lights - they can really make your day!