I sweat loads too, mostly from my face, which is even more embarrassing!!
Luckily my school didn't have uniform but I have had other times when I've had to wear official things and sweated so much it's obvious
I used those sweat pads in the underarms, both the disposable (stick on) ones and the ones you sew in. Also a t-shirt underneath, which I know sounds like it would make you hotter, but absorbed the sweat more - you can get some very light ones - so I would be less bothered by it. And my sweating wasn't just from heat anyway so two layers didn't matter that much.
Different deodorants - I didn't find the prescription ones helped much but there are others, various 'clinical strength' solid ones that don't sting at all, think they're American but you can get them on amazon. Also various creams that you can out on to block sweat glands for a time.
And bringing a change of clothes, even if it's twice a day, carry and extra shirt or two in a PE bag, would be the end of the world. But with the sweat protectors, you might not need them that often.
Also I teach teenagers, and some of them arrive very sweaty, and don't seem to mind - seen as more of a sporty thing! - so maybe they're more tolerant nowadays. They seem to look after their friends more than used to be the case, and defend them for things they can't help.
Much of the year she can keep jumper or blazer on anyway.
So no, I wouldn't choose the school based on that. If there's teasing, it could be over everything. I'd try to go in assuming it won't be a problem, and only consider changing schools if it really was.