She may just be a small person. Has she had her growth spurt yet? My dd is a little bigger 80 lbs, and she is 4"11". Same age. She is the smallest in most of her classes. If she not growing @ all then there is a problem, but as long as she is making some progress even if it is little she should be fine. If you are really concerned, ask her dr.
P.S. She is already taller than my grandma. LOL
at 1:18 PM on Feb. 23, 2009