Your baby has taken Antibiotics for 6 days, and if she is not getting better, you must take her back to the Doctor. The Doctor has to rule out some Asthma
,allergies or other lung diseases.
The low intake of milk is not so much worrisome, if she is not losing her weight. Did you change her type of milk? it seems you are not breast feeding your baby, and your baby is on formula milk, which is not preferable.
I hope that you are aware about vaccine
against peumonia, and haemophilus influenza
. You must give to your baby these vaccination
, once she is better.