Magnets. They have special sets call Magnetx (or something like that) anywhere, Walmart, etc. My kids love them, especially my 3 year old. He'll play with them for hours if I let him. It's like working with legos and building all kinds of things, but with magnets. They would be near the legos section.
My daughter also has a magnet board, with little strips of colored magnets that she can "draw" with. We ordered them from a catalog in the mail. But, I'm sure they would something of the sort at Toys R Us or somewhere. They are really neat. It's like working with paper strips, but they are magnets that stick to the board.
They also have kits that come with a drawing easel/board. It comes with markers, crayons, paper, etc. All compact and fit inside the easel box. Like a briefcase.
Small electronic games for around $10. My kids like solitaire. But, they have others that a 3 year old could grasp the idea, I'm sure. My 3 year old has a little laptop computer with educational games on it. His is Thomas the train. But, I've seen Barbie ones. It would be educational and have tons of stuff for her to do.
Buy a stick(s) of glue. Give her construction paper. Have her rip it up into little pieces and glue different shapes and colors on a larger sheet making some type of picture that she has to cover most of the sheet with. That would be fun. My daughter would love that!
Also, Hobby Lobby has a toy/kid section with some really great stuff that you don't find anywhere in a toy store.