Can you take her to a pediatrician and get her weighed and get some advice?
Is the dr concerned about her weight?
If your baby is refusing to eat, or cries everytime they get the bottle- then it might be the type of bottle you're using. That happened to my sister as a baby, and my grandmother used a old baby bottle which git her to eat. If your breastfeeding then maybe your baby needs a combination of breastfeeding milk and formula because she might not be getting enough food
Some babies are just slimmer than others. Is your pediatrician concerned about her weight and size?