Daniella, are you sure she's hungry? she might just be wanting to suck maybe. Have you tried a dummy? they dont always work and some people don't like using them for fear of future problems but i persoanlly consider it a lifesaver at times.
Either way, absolutely do whats right for you. There are no rules when it comes to having kids you have to do what work for you and your baby, and every child is different.
Just a thought on the possibility of her being allergic to the formula, which one are you using? I wouldn't use the gold varieties because they are heavier and don't always settle too well in newborns. I had the same trouble with Dylan when he was 2 months (he was formula fed from 2 months) also different brand have a slightly different make-up of ingredients so you might try a few different ones til you find one that agrees with her.

Anywho, i've gotta go save Ryan from DH trying to use controlled crying on him.....