This definitely sounds like a problem you may need to approach the doctors with. If she's truly not eating sufficiently for a long period of time, you need to find out why; there are some conditions that manifest as an unwillingness to eat. She may also be allergic to something common which is causing digestive upset. On the other hand, she may just be growing; it's very complicated to judge this sort of thing without data.
The way to approach your doctor is to keep a food/health journal for your daughter. Write down everything she eats, and is offered. Get a scale and actually weigh the food if needed to accurately describe exactly what she is eating. Entries like:
- 2/5/2015. Woke @ 3am, 5am, 6am; stayed awake after 6am. Complained about legs hurting.
- Breakfast (7am) : 1 scrambled egg, orange juice. She ate about 1/4 of the egg and drank one sip of the juice.
- Snack (10am): 1 fruit bar, water. She drank half of the glass of water, and ate about half of the bar.
- Lunch (12pm): About 75g ham, a slice of bread, a slice of Cheddar cheese, milk. She drank most of the milk, but didn't eat any ham or bread. She did eat half of the cheese slice.
- Snack (2pm): One apple, water. She drank 1/2 the glass of water and ate one slice of apple (1/8 slices of a medium apple).
- Dinner (5pm): One lamb chop, mashed potatoes, green beans, and water. She drank the whole glass of water and ate most of the lamb chop, two bites of mashed potatoes, and three or four green beans.
- Dessert (6pm): A small bowl of blueberries (30g). She ate two or three blueberries.
- Her mood for the day was quiet; she played outside some but did not want to play with others. Two emotional outbursts but neither serious. She went to bed without very much fussing.
That would be a reasonable journal for the day. Keep that for two weeks or so, making sure to have every single meal fully documented, and notes on how her mood was, how she slept, how her bone pain felt (where it hurt, how often she complained, etc). Then take that to the doctor, and use the journal to show him/her exactly why you are concerned about your child. It's very common for parents to come to the doctor with "My kids won't eat", but often they eat fine: so you need to get enough information for the doctor to completely understand why your concern is a legitimate concern, and to be able to judge what the right action is.