I'm already partial to Greek names. And I already think Riley (especially with the original spelling) is more masculine than feminine.
It's curious that your friend is torn between the two names, because I recall, as a kid (when I was a big fan of the Olsen twins), watching Mary-Kate & Ashley play twin sisters named Riley & Chloe on *two* separate shows / movies.
Please rate my personal name lists:
www.behindthename.com/pnl/69381www.behindthename.com/pnl/69381/109399www.behindthename.com/pnl/69381/91835http://greens-end.myminicity.com