Hovering MIL

So im 31 weeks pregnant today. I had my 30 week checkup yesterday. My MIL constantly asks if they've gotten a weight on my son yet bc im in my third trimester. She doesn't believe me when i tell her you pretty much only get 3 scans when you're pregnant: dating scan, anatomy scan, and a mid third trimester growth scan. She literally argued with me over it yesterday then tells me that i look little therefore my son is gonna be underweight. I was 135 pre pregnancy. I weigh 153 now. Bc of my "child bearing hips", they've done nothing but get wider and wider, instead of my belly poking outwards. I explained that to her as well. How do y'all deal with a hovering MIL? It's like she doesnt ever believe me when i tell her my bump is measuring perfect and so is baby (they of course measure me with a tape every appt as well as do a doppler). I didnt tell her that im at a risk for lower birth weight bc of my epilepsy medication (i start getting growth scans every 4 weeks starting the 19th), but that it isnt really much of a concern as of right now. Do i just need to tell her straight up to stop trying to stress me out? I also miscarried 2 months before getting pregnant with my son and she acted like that pregnancy never even happened, and that my d&c wasnt major, but her son getting a freaking hemmorhoid was major (he also didnt sleep for days after finding out about our loss, but slept like a baby with a hemmorhoid lol). My fiance has told me time and time again not to worry about her opinions, but it's hard not to think about the way she thinks or acts sometimes.