Question: How to deal with a Pushy Parent?

One of my new students has a mom that is basically a lovely, caring person. Mom wants to  attend every lesson with her eight year old daughter.  I appreciated her interest and support, but after a few lessons this mom began bringing a hymnal and several new pieces of music to lessons that she wanted her daughter to learn.  Her daughter has has only one year of piano, and is barely able to play even the easiest beginner material hands together.  Mom insists her daughter is very capable, learns fast, and surely will be able to play hymns for her chuch youth choir very soon. This sweet child reads poorly, has no understanding of basic rhythms, and is understandably insecure and reluctant to play anything with confidence. How do I tactfully ask mom to back off?   What would you do?   --Frustrated