Hun we went 11 days here once. With fully bf bubs I believe 3 weeks is the upper limit. In fact I think I read that somewhere in the ABA website and my GP who is also a LC confirmed it. I wouldn't give her prune juice it may just upset her tummy. If she isn't seeming constipated and seems content I'd let her go a little longer before trying anything else. You can always try cycling her legs and gentle tummy massage in a clockwise direction.

HTH
Spring