Eeep, I do know how you feel, with the whole small hands deal. Acoustic songs that I enjoy playing (and don't think they are too terribly hard for either a girl or boy) are:
"You Were Meant For Me" -Jewel
"The Closest Thing" -The Juliana Theory
"Blackbird" -The Beatles
"Wonderwall" -Oasis
"Let Her Cry" -Hootie and the Blowfish
"Building a Mystery" -Sarah McLachlan