Hi Kate -
Aren't moms fun?

I have two moms in my life and within months of my surgery, both of them ended up living within 30 miles of me and each other. It's really making holidays and family visits a giant mess.
My own mother is very supportive - in fact, she was my dad's support surgeon for his surgery (MGB - mini-gastric bypass) and then was mine, since my hubby started a new job a week before my surgery date. She knows more about ghrelin and bypasses and vitamins than any non-op I know. She even keeps me supplied with foods I can eat, and she is aware that those foods may change from week to week. But until she sat through a few classes, she didn't really get it. It took having a guy with "M.D." behind his name to explain to her about hormones, malabsorption, and potential post-op issues for her to get fully on board.
My mother-in-law, God love her, doesn't get it at all. She loves skinny people and she wants me to get that way, but she just doesn't get surgery. Every time I see her she asks if I'm hungry. Some of it is just cultural disconnect - my daughter is vegetarian by medical necessity, and Grandma kept trying to feed her burgers and bacon. So it's not just me. But she is convinced that if people would just eat better and go for a walk, they'd get skinny. Because she is naturally thin, she has no idea.
My July 4 was me not keeping anything down all day (stress, most likely), but trying to make my own tiny dishes; my mom all worried that I wasn't keeping anything down; kiddo and I trying to explain that you have to grill the veggie burgers BEFORE you grill the meat ones or the urea from the meat will get into the veggies (kiddo can't have uric acid - kidney stones); how cheese is good for me, bad for her; and how no, I'm not hungry, I am not going to starve to death, and no, really, neither of us wants a hot dog. Sweet tap-dancing Moses on a cracker.
And I'm not especially high maintenance as a rule. Gack.
All that tl;dr post is to say that your mom might really get on board after a seminar, or she might not. If she does, awesome. Makes life easier. If she doesn't, will that keep you from having surgery? For me, it wouldn't. I'm always going to have to deal with people who don't understand my stomach or my weight. I just traded "ooohhh, why don't you just eat right and get thin" for "aren't you hungry? I'd just be hungry all the time if I ate like that", and I'm okay with that.
Good luck with your journey toward health! It's pretty exciting. What surgery are you looking at?