My son is 15, weighs 107 pounds and is 5'4". He is the slim and almost a head shorter than his friends, and was shorter than his last girlfriend. He really doesn't mind at all.
He has always been one of the "smaller" kids in his grade, partially because he is a June baby and started school as an early 5 year old, and partially b'c of genetics. I am only 5'2" and while his father is average height, he is slim build.
But, he did grow tremendously between 13 and 14, and seems to be on a steadier, though slower, growth pattern now. His pediatrician has told him that it would not hurt to gain weight, but has also made it very clear to him that he is healthy and normal.
He is also not a great meat eater. He prefers poultry and seafood over beef and pork, eats veggies and fruit, and drinks milk and loves peanut butter.
If your daughter is happy, accepted by her peers, and has a good self image it does not matter how tall she is. With my son, I found it more important to teach him self acceptance than dwell on the fact that he is "small". He likes himself for who he is, and that means so much more. Confident people attract other people to them. So it all evens out.