Little girl friendly versions of Linux (or themes for Linux)

QIMO 4 Kids

Qimo is a desktop operating system designed for kids. Based on the open source Ubuntu Linux desktop, Qimo comes pre-installed with educational games for children aged 3 and up.

Or Edubuntu, "Linux for Young Human Beings" (Ubuntu customised for educational use):

And slightly off-topic: OOo4Kids is an educational project. The idea is to provide software for 7 to 12-year-olds, based on OpenOffice.org source code, say, extremely simplified.

The Sugar desktop is plain and simple, used for the OLPC program.

Just to record it here, there is also a pink fluffy theme for KDE 4.