hold off.
if its making you feel uncomfortable and she does eat just small amounts and does drink daily then thats not to bad
my DD who is 24 months only weigh 10.2kilo and was always in the 50th percentile she is now just in the 3rd
she eats some days its alot others not much, she has only this week eaten breaky every morning and eaten half her dinner we dont serve her big meals, but she will graze all day on fruit and cheese.

maybe try getting her to feed herself make it a game teach her to count using carrots say eat 2 carrots then count 1, 2 or something so she doesnt think she is eating but is if that makes sense.