Toddlers Hair

Not conditioner.
What hair she has is too fine for it, and conditioner can clog scalp pores.
You can massage olive oil into her scalp maybe once a week then wash it out.
It's safe to use for cradle cap (not that she has any) and it's good for the skin.
Searching Google for '3 yr old still has no hair' comes up with a lot of information.
It's not an uncommon problem.
You need to take her to a dermatologist.
The sparse hair may be due to some form of inherited disorder causing poor hair growth or a hair shaft disorder, or may just reflect slow hair development.
But a dermatologist will be able to help you figure out what's going on and the best course of action to treat it.

In the meantime, get her a book called 'Melisande'.
It's about a Princess cursed to be bald by a grouchy fairy who eventually overcomes it with a wish but there are exponential difficulties when it's growth gets out of control.

http://www.amazon.com/Melisande-E-Nesbit/dp/0763607177

I would see a pediatric dermatologist.

My son didn't have much hair before 3. My daughter has a head full of wavy fine hair that tangles horribly. I recently starting using Burt's Bees Shampoo and California Baby conditioner. The conditioner you can safely leave in for curly hair, dry or frizzy hair. Its an all natural product so I feel pretty comfortable leaving it in.
I have noticed a HUGE difference in the appearance of her hair since then. No more tangles much, and the ones she gets are easy to pull through. It's so shiny and smooth feeling now.
Anyway, hope this helps.

If your really thinking something isn't right, you could take her to a dermatologist , just to make sure.

neither of my kids had hair before 3.

If your pediatrician thinks it's fine and you've trusted his/her judgement in the past, then it's probably just fine. But if you're really that worried, I agree about getting an opinion from a dermatologist.

It's very normal in my family to not have hair between 2-3 years old. I myself was pretty bald until 3, and now have really thick hair. My daughter is 2.5 and her hair is just finally starting to come in. My son is about a year and you can see the glare off the top of his head :)

Maybe try buying her some 'princess' headbands or wraps that she can wear!

I would start using conditioner on her scalp, a healthy scalp equals healthy hair.

My friend's daughter had hair like that, virtually no hair at 3+ years old. It eventually came in beautiful and thick. If your pediatrician isn't worried, I'd just give it time.

What does the pediatrician think?