I have two SW CAH boys,  my youngest now 6,  did not eat anything for 2+ years,  really skinny,  just drank milk....It drove me nuts with worry.  Anyway at about 4 years old(ish)  he started eating everything.  He loves everything now,  I have started having to limit what he eats at snack time.  Still slim but I did not want him to get into bad eating habits.  I never made a big deal out of eating,  I just offered him what we were eating.  If her levels are OK try not to worry,  I know it is easier to be on the thin side than dealing with losing weight.

Good luck to you.