User blog comment:XxDragonHeart/Daphne's Age/@comment-4074115-20140520050304

Her body didn't age during her time as a spirit, so she's still young.

As an interesting side note, there's also a fan theory (don't remember where I read it) that when she sent Bloom to earth, she actually sent her forward in time a little, and if that were true she would really be even older!