It's ok. We'll take her. She just won't leave boot till she passes the swim.
Basically, tell her to get her ass in the back of the line if she can't swim very well. You'll jump in the pool and tread water till your whole class is in the pool, one person at a time off the 5ft (or whatever it is, I remember it being higher) platform. Once you're all in the water together they tell you to swim to and line up on a cone at the side of the pool. Ready? set, go. swime the entire pool, all four sides without touching the sides or the bottom and you pass. It really is not all that hard. You can swim in any position you like, as long as you make it.
I wouldn't worry about the physical fitness part of it for her. They'll whip her into shape, regardless of all the shit the other services give us.