Definitely depends on what your DD is into! Some more generic ideas are

Teddy bears picnic
Mad Hatter's Tea Party
Theme around a nursery rhyme - Gingerbread man/Twinkle Twinkle - for cake ideas etc
A letter party - so things with the first letter of DD's name
A Pink party - Pink food/decorations/dress

HTH - Have fun and Happy birthday to your DD!

xx