Well she finally went twice
Even formula fed babies need to have a bowel movement every four days. Breastfed babies usually go more frequently than formula fed babies the first month or two.
It could be the formula or if you breast feed it could even be your milk because what you eat she eats and it could be making her constipated I would tlk to her pediatrician Congrats on your baby (=
Its normal for some my daughter had that problem...i would see her doc for suggestions.... we had to switch formulas..
I agree, definitely talk to her pediatrician, she should be (at least) going every other day, probably more like at least once a day.
Even if she is exclusively breastfed, she should be pooping regularly at this point. You definitely need to call the pediatrician.