I'm surprised this thread is so long. While there is nothing inherently wrong with exiting a ride, the only I time did it with a FP was under the old FP system on a slow day. I was able to get another one five minutes later. Under the NEW system, giving up a FP in MK is a much bigger loss. MK has many fine FP options, and guests are now so very limited in the number they can obtain.
It isn't for me to tell the OP what to do, but in answering her question, it bears mentioning that she's making a big sacrifice for a small return. The queue of Splash isn't one of the exciting ones, and no matter what- Splash is a relatively long ride. My old guide says 12 minutes.
If I was in her shoes, I too would prefer to use my FP elsewhere.
I find it odd equate her choice with morality. I can easily bear to be apart from my spouse for half an hour. Further, even if she doesn't use her FP, she can still meet him at gift shop at the end of the ride.
By all means though, she is free to do it.