When a child is learning to speak, pronunciation and grammar are not what's important. First, you want to get to a place where you can understand what your child is trying to say.
At the learning stage, it's more important for your child to feel that he has successfully communicated to you. Corrections can come later on, when your child is talking more comfortably.
This is also a good time to reinforce what she was trying to say, so that you can provide her with a model for her speech. For example, if she says "I aw itty go," you say, "Oh, you saw the Kitty go".
If you are concerned that your child's speech isn't improving, you may want to ask your child's doctor to refer you to a speech therapist or speech-language pathologist. Or you can call the Canadian Association of Speech-Language Pathologists and Audiologists at 1-800-259-8519.