Orly, I'm sorry about your family issues and hope all turns out well. Last thing you need is someone with an over-sensitive snout giving you grief.
I go in clean every day, often hair is still wet from shower. Before it dries it's already wet with sweat in this weather. Before break, even, I can tell that I'm less than fresh but it's an honest sweat. Sweat flushes impurities from our system and isn't meant to smell sweet. geesh
I worked with a young man years ago who had a problem with smell. You could tell he was a neat and clean man, just had a scent. Some folks complained and made fun but I always pointed out that he surely couldn't help it. He didn't smell like sweat, rather an acrid, chemical smell that he just plain had. Don't know if there is anything a person can take to control that or not. Is there someone you trust that you could ask whether it's a plain sweat smell or something stronger? Either way, it's your body and you needn't be ashamed of it.
I have also worked with a young man who farts and stinks on purpose. He is at least 30 years old and acts like an eighth grader. I told him his sphinctor muscles were going to wear out from all that forced farting and that in several years they would be so weak he'd lose control and be crapping himself. After continuing to endure his stench I finally lit into him big time. He bawled to management and I was told to be nice but something clicked in him. Suspect he was talked to by a sup. He still farts around some of the others but does not do it around me.
Changing clothes during break is absurd. I would certainly tell the sup that her comments are offending you and to please stop the harassment. If she opens her mouth again, I'd go higher up and take a union rep along. Best of luck with this. So sad that you are criticized for this when you're working your butt off for them. Again, best wishes to you and your family. They are so much more important than anyone at UPS.