Hello Samantha and welcome!
Perhaps a larger nipple size would help? My son at around 6m liked a Y cut nipple for his formula. Maybe in a sippy? Some babies just don't need/want a lot to eat. Could she be teething? What does your pedi think? Is she gaining well, etc? I think you should discuss with them about adding anything to the formula - but when I transitioned to milk, for a while we used a tsp of vanilla carnation breakfast in 8oz of milk and then slowly put less and less of it in. Perhaps something like that would work - but again, discuss adding anything like that to your baby's diet with your doctor first.
HTH some!
Zoey