I know you have a zillion responses but I wanted to echo what one other person here said and that is that too many toys can be overwhelming. You said "She has every toy and activity in the world"
My son did too, until I got tired of the needy whiney behavior. I did three things and I got a whole "new" child.
1. NO tv or movies.
2. no juice between meals.
3. here's the biggie: I took away and stored or gave away almost ALL his toys. I left him with a few matchbox cars, his building blocks, books, some paper and markers, and a few other favorites.
You would just not believe the difference! He was calmer, happier, more independant, WAY less whiney and needy, and his ability for imaginative play just took off dramatically.
Now I try to weed down his always-growing collection of toys from time to time, and cut down on the tv time when I start letting that get out of hand. These actions aren't punishments! They are tools to help my son be the happy healthy creative little guy that he is. These days he is happiest with a couple of cardboard boxes and a stuffed animal.
If it seems extreme, maybe it is, but it was amazing how it helped us. I would encourage you to give it a try.
(P.S. my son was a little younger when I did this, you may need to do the toy-removal differently than I did, and not just take everything all at once. At his stage in developement, I did not need to explain what i was doing or warn him ahead of time. He is almost three now, and the last time I did a toy-removal and movie-ban, I explained what I was doing and why, and encouraged him to choose a few favorite toys to keep out and to select his favorite books to read instead of watching a movie.)
If you do this, please send me a message and let me know how it went :)