I got my niece (age 5) a barbie doll.

Is she a girly girl? What about clothes, bags, shoes, hairclips, necklaces "dress up" type costume jewellry.

Stuff for outside, eg a skipping rope, balls, pogo stick, that tennis ball on a stick thinggie (can't think of the name).

Is she interested in flowers or gardening (beyond making mud pies)? Maybe her own seedlings to grow.

Ummmmm. I will have this problem too in a few years