Not OP, but- she’ll have lost some mass, but it might not be a noticeable amount. The uterus is a super adaptable organ: depending on what stage of menstruation, pregnancy, or neither, the uterus can range in size from a chicken drumstick to a basket ball.

She also will have been NPO (nothing by mouth - no food or drink for around 12h before the surgery), so her weight going in was likely lower than normal; and had an IV pumping saline into her during her operation / waking up hungry as fuck and now with the green light to actually eat… so, she may have actually gained weight just by returning to a normal state of satiation and by being super well hydrated.

Source - I’m a surgical tech. I’ve assisted in probably a hundred or so hysterectomies, and have physically handled the specimen after it’s been removed in nearly all of them.