We had to take swimming back in high school also. While it wasn't co-ed, it was very demoralizing. We were not fortunate enough to be able to wear our own swimsuits, but were issued a school one made of cotton knit (similar to a wet T-shirt) that did not hide anything from view. There were very few people who could wear them without being horrified. If that wasn't enough, our female gym teachers made us strip them off and wring them out in a clothes wringer in the shower area, while they stood and watched us. (We were convinced they were perverts.) I still have bad dreams involving high school to this day.
My kids had to take swimming also, but of course they were allowed to wear their own suits, so at least they were somewhat more comfortable. I do think while it may be hard for your daughter, it's just one of those things in life that you just have to suck up and get through it.
At my high school we were allowed out of certain PE classes if we did other things. I got out of regular PE for running in a 50 mile club and out of swimming by teaching a swim class. My kids were exempted when participating in team sports during that particular sport's season.
