A lot of nasty, bullying posters on form I think I this thread. At no point has the OP been rude, she's been nicer than I'd have been! Sorry you've had this pile on, OP. Some just enjoy being knobbish. Ignore.
Anyway - lots of people missing your point, which is simply that people who have always been slim/pretty have no idea how it feels to be overweight. I've been at both ends of the scale, and you're right.
You're not saying that slim/pretty people don't have any problems ffs, or can't suffer with awful self esteem or dislike how they look - of course they can.
But there are definitely experiences that an overweight person has, that someone slim just won't have.
Can you be blunt with your friend and say "it makes me feel shit when you ask what I'm wearing."?
For a slim person, choosing an outfit is about what you fancy wearing that day, what's appropriate etc. For a bigger person, it's also that but also about finding something that just bloody fits and looks even half okay and hides all the worst bits you dislike about yourself, only to stand in front of the mirror feeling utterly hopeless realising there's no magic outfit that will hide the size you hate that you are.
It erodes your confidence and self esteem even further.
Although I'm slim now and I might still 'feel fat' in an outfit or have a bad day, it's nothing compared to when I was a size 22 crying in the changing room when a top I liked on the hanger looked bloody awful over my supersize boobs and overhang stomach.
Self-hatred is not limited to overweight people, but there are experiences a bigger person will have, like being called names in the street, declining invitations because you really have nothing to wear, the stares from strangers when you're at a restaurant, being immediately judged as lazy and greedy when you meet someone, to name a few.
My confidence has improved since losing the weight and getting fit, but not only because I look better - people treat me better and no, it's not because I feel better and giving off better vibes, it's because people don't make those judgements anymore and they're nicer to me. Slim people won't encounter that. They may well encounter other judgements, of course! But not due to their weight.
You can't 'know' unless you've been there.