Talk to your doctor before you do anything. Many breastfed babies don't poo for over a week at a time (it just all gets absorbed) and many children and adults are "once a week'ers". Not everyone's metabolisms are the same. I know it freaks out people who poo every day (I can't COUNT the number of kids I know whose parents shove enemas up them every day because the PARENT is a once a day pooper, but the kid naturally poos once every couple days to once a week). I myself only poo once or twice a week max, my husband, otoh, is in the bathroom at 10:20am and 9:45pm every single day.
New babies are also "learning" how to poo. The pushing and the learning process of contracting those smooth muscles in a fluid/efficient way is an important part of neural development.
If she has somewhat hard poos... just put a little vaseline on her rectum to keep it from tearing (little tiny cuts, not like episiotomy type tearing). It's like moisturizing chapped lips so they don't crack when you smile.