I was going by your statement in the thread for my response.
But by switching Ven and Ariel's hearts, you just made Ven a drag queen! D': (I'm joking, just so you know.)
In all seriousness again, I don't think it's possible that the two switched hearts either. Hearts contain memories and had the two had their hearts switched, then Ven would have memories of being a little girl with a fish tail swimming in the ocean and Ariel would have memories of being a young, teenage boy fighting Unbirths with two older teens and getting his butt whooped by an old, tan guy and a strange guy in armor. Just saying.