Look for eduactional toys specifically aimed at 4-6 yrs old. She will be able to understand them and they will leave some scope for her to be stretched too.

Jigsaw puzzles are good as the outcome will be the same but she will get quicker on the completion and feel a sense of achievement. There are some very chunky wooden types that suit that age group, possibly incorporating the alphabet or numbers in sequence.

Is she starting to read? Books to read, books to colour, books with pages of stickers to fill in the pictures.

Beads for threading on elastic and making necklaces/bracelets. Excellent for co ordination and a pretty end result.

Fuzzy felt story boards, where she can use her imagination to create different scenes.

A blackboard and chalks. She can experiment and rub out and start again. She will feel like a teacher!

Packets of seeds to plant and grow, something that won't fail. I don't know where you are but kids love sunflowers, they are bound to take and the end results are impressive and of course she learns by tending and watering them too.

Maybe something that she thinks of as 'grown up' for her room? A glittery disco ball to hang from the ceiling or funky bedding with her fave charcaters on. A personalised cushion maybe or even a groovy clock to learn the time, they do some fab ones aimed at the younger market with swinging pendulum legs etc.

Hard plastic stencils of flowers etc, she can get instant results and practise hand eye co ordination too. Her creations will please her and she can use them for making cards for family and friends.

I'm sure others will have lots more ideas. And I am sure she will love whatever you choose.