TFC,my Mother is like your MIL. She once had a birthday party for me and told me to be there at 7:30. I told her we would be there at 7:45 as we were eating dinner with my in-laws. We got to my parents house at 7:45 and no one would speak to us. They had already eaten the cake and she threw a wrapped present on the table angrily. She said,"Young lady,IIIII am your MOTHER. I should not have to wait 15 minutes so you can spend time with your in-laws on your birthday. You are MY child,not theirs"!
My H is a no nonsense man. He took my arm and said,"We're leaving and don't you EVER treat her like this again". She was really stunned and tried to back pedal but we just left.
I've been in IC many years because of my Mother. She ruined my wedding and the day our son was born. Because our sons first name begins with a "D" and so does my FIL's name,she decided we named him after my FIL and didn't get my father's name in there. She threw such a fit at the hospital, the nurses asked her to leave.He was not named after anyone but no one can reason with her.
I used to go crazy with her but what I learned in IC is that my Mother is stuck in "child". She's very petulant and manipulative. My brother has not spoken to her for 30 years.
I think you did a good job under difficult circumstances. Your MIL is putting a guilt trip on you. My Mother is a bully and tries to put guilt trips on me too. Thank goodness for my counselor. My counselor once said to me,"If your Mother dies,it's NOT your fault". My Mother would use the "You'll be sorry when I'm gone" guilt trip a lot.