All three of my boys did this as well.
Try giving her just one word to say when she wants something. Like if she wants a drink and she says, "Uhh Uhh" or "Ooh Ooh". You say, "Use your words. Say CUP." Hold the cup in front of her and repeat the word. If she even tries a little bit to form the word cup, clapp your hands and make it a BIG deal, praising her, and then hand her the cup. If she just yells her normal sounds - don't give it to her.
I still do this with my almost 5 year old twin boys and my 2 year old boy. If they want something, they have to say, "please mom can I have my cup?" (or for my 2 year old: cup mama? please?)
Hope this helps! Best wishes to you from a mom whose been there :)
at 8:27 AM on Oct. 4, 2008