My daughter doesn't poo everyday maybe every other day but doesn't show signs of constipation so I'm not worried.
My little boy is on Movicol because he doesn’t poo for like 4 days and sometimes when he does his in massive pain with it and hurts him! But yeah movicol does help a lot and is safe it’s never harmed
Movicol is a stool softener so helps soften things to help them pass it easier. Is your baby comfortable pooping every 2-3 days or does she show signs of constipation? If she isn't uncomfortable or passing very hard stools, I wouldn't be concerned.