My heart aches for you. I too have had surgery "suggested" to me too.
It hurt my feelings somewhat because my fat seemed to bother them more than the danger of surgery for a person of my size.
I know there are a lot of people who have had success with it... but I also know a lot MORE who have had problems with it.
Just remember that your MIL is "probably" listening to the media about all of the successes and she is truly trying to be helpful. At least I hope so.
Either way.... you do what is best for YOU. Jana gave you lots of good suggestions. Finding the right food plan.... WATER... exercise. Gee... where have we heard that before. LOL
There is no secret... just COMMITMENT needed.... plus a little enthusiasm and determination.
If hunger is your problem... I have found lower carbs help a LOT.
I did NOT say "no carb"... just low carb helped me.
But that is just me... find what works for you and then stick to it... we will be here for you for support.