I don't have tons of experience with my own children yet (my little boy is 18 months) but I worked full time in a preschool for children with Autism....and we taught parents a behavioral technique that worked well for ANY child with negative behaviors. The first thing to do is praise, praise, praise the positive. Anytime she listens to you, no matter how small the act is, praise her a LOT. It takes 10 positive comments to undo 1 negative comment. So lay it on! :) Also, we taught parents (and used this with the children in our classroom) how to cut back on 'nagging'. If we want the child to pick up a toy we say "Sara, please pick up the toy." Give about 5-10 seconds for them to respond, if she doesn't listen say "Sara, you need to pick up the toy" again, give 5-10 seconds, still no response "Sara, this is picking up the toy." And YOU hand over hand, help her pick up the toy. If during any of the first two requests she picked up the toy on her own, then praise her a LOT for listening and following directions. If you had to help her put it away, don't give praise, but just use simple statements. "This is putting away the toy, thank you for putting away the toy." etc.
This technique allows the child two chances to follow the directions before they know you are going to make them do it. Eventually the kiddos learn that they are going to have to do it and doing it right away is easier AND they get a lot of praise for it.
Consistency is the most important tool here. It only takes one time of letting her get away with it, and then you are back to square one. So be consistent in following through with the action. Good luck!!!
I hope that helps. I have a lot of experience putting together more detailed behavior modification programs...so if you need more help let me know. :)