If she can ride Everest, I think she can ride Splash.
It took me 5 trips to work up the nerve to ride SM. I hate drops, but my husband kept telling me it was the best ride at MK, and I had to see the interior. When we got to the lift hill leading to the drop, I definitely was starting to freak out. But then I looked into the distance at Cinderella's castle, raised up my arms and screamed as the log took its 2 second plunge down to the bottom. I think screaming really helped me. And afterward, I felt amazing. I was so, so glad I'd done it, and I love the ride now. The drop doesn't faze me (much).
Honestly, I think the backwards section of EE is more intense than the drop in Splash. You do feel the Splash drop more in your tummy than you do on BTMRR or EE, though. And there's a small, dark drop in the middle of the ride that comes as somewhat of a surprise. That one almost bothers me more because you can't see anything. You might want to show her the ride-through on
youtube and see what she thinks.
As far as the water goes, you will likely get somewhat wet, so you should go at the hottest time of the day. I've never gotten soaked, but I've certainly seen people come off the ride whose clothes were pretty soggy. It really is kind of random chance.
Good luck! I hope she works up the nerve to ride. It's such an amazing experience!
