Lots o' treats
Haha, pretty much - try and make it a fun experience. Lots of rewards for being well behaved, and soothing words to keep her calm and happy. Keep the baths short in the beginning, so she doesn't get stressed out right off the bat. Over time, you can lengthen the time you spend washing her ie: shampooing mane and tail, lathering up her whole body. Just start off with light hosings and short times in the water. Eventually, she'll grow to enjoy it.
Have a good time at camp :)