I would go with the larger to be safe.
Is she growing at all anymore...??? What age is she...???
It's always hard to know what to do, as some boots while the same size internally are actually a different footprint size on the outside... And hitting that middle ground sucks...
I had that with K2 bindings when i 1st started, and could never get comfortable with either side of the spectrum, so switched bindings where i was bang in the middle of there size guide for 1, and it made a huge difference...
Height 5"11, Weight 200-210lbs, Born 1969
Regular Stance, Ability NOT GOOD
2012/13 114 days
2013/14 102 days
2014/15 57 days and counting
K2 Fastplant 154, Ride DH2 158, Endeavour Vice 155, Signal OG 155, NS Evo 157 (Stolen), Flow Quantum 155