Something you think is a little too old for her. (Only a little) Little girls love to be treated older than they are.
All my 4 yr. olds girls at school want Dora the Exploror back packs, fuzzy blankets and shirts, toys..you name it. There are so many Dora DVd's too.. the kids watch & love everyone..
I would get her something she can plant and watch grow.
a birthday card with the number 4 on it......sorry ,couldn't resist it :-)
In my experience, unless you want to go educational, then get something that moves around a lot and makes lots of cool noises.
A Ice Cream Cake
a barbie! =)
How about a good picture book - or a book suitable for her age? My mom started me reading when I was very little and it has been such a blessing. A love of reading can really do a lot for you, and you can encourage it with a book gift. Something fun. There's tons of good stuff out there for all ages.