Are we overdoing it?

Question
We haveth had our guinea pig for about a month. She is very fond of lettuce. If she hears the refrigerator door opening or rustling in the kitchen, she will stand by the door of her cage and look at as hopefully and squeak imploringly. When we give her some lettuce, she does a little dance of joy and gobbles it right down. How much lettuce is too much? The information we have found on the internet and in books is somewhat confusing. She has a good appetite and eats plenty of her pellets. She also gets a small amount of mixed greens several times a day.

Thank you!

Answer
well as long as it is not iceberg lettuce then in theory as much as she can eat. if her stools start seeminging a little loose then cut back, but otherwise feed her all that she wants, mine live almost entirely off grass and are very fit and healthy, lettuce shoul not be that much more rich or watery. just avoid iceburg and you will be fine.