My son was just the same......I was saying no all day long. I made sure that my home was completely baby proof--there was nothing he could get his hands onto that he wasn't allowed to have. Then at his 15 month check-up, the doctor told me that there did need to be some limitations to his environment so that we coudl introduce discipline and teach him that he is going to have limitations sometimes. And one more thing the doctor said: TIME OUT. I never thought at that small of an age, time out would do anything. I set up a pack and play in a corner of the room, and all it took was one or two time outs before I could just say, "No or you will go in time out", and he listens. It was like magic! Now the pack and play is out of sight because just the mere mentioning of time out gets him to stop whatever it is that I don't want him to be doing.
Good luck! And always, no matter what you do, BE CONSISTENT!!! That will get the fastest results of anything. It sucks saying no all day long, but she is listening. Believe it or not, it is comforting in a way to hear that word "No" from you every time she misbehaves because you're acknowledging her and producing a predictable response...as odd as that sounds. She knows you're looking out for her.