I'm going to be honest here. It's not about the "stealing a boys name" thing.
My cat is named
Riley. My mom came up with it because she kept saying, "He has the life of
Riley," which is apparently some Irish saying that means he's spoiled basically, and it just stuck. I've met soooo many other pets named
Riley, male and female.
I don't mind
Riley that much on a guy, but on a girl I just think of a disgustingly unisex/bland name. Think about it. If you saw the name
Riley, you wouldn't know if it was referring to a human or an animal let alone a male or female. Plus I just think it sounds extremely unfeminine in general.
I know it sounds harsh, but honestly, if you like the name, I think you should use it on a treasured pet, because it's really trendy right now. I've resigned a few names that I like as good pet names. For example, I'd probably use
Sophie on a Cockatoo because
Sophia is too popular. But cockatoos can live 80+ years, so I think that's an appropriate use of a good name.
Ryleigh does look a little more feminine, but it also looks fairly creative and trendy. I wouldn't use it personally because I don't think it will age well, but it's not terrible. I'd prefer it to a female
Riley.