Where do you live that has bears that large?
Since your GF shoots a Marlin 336, she might do well with a Marlin 336 SC (Sporting Carbine) in 35 Remington. If you reload, you could use 180 grain Speer FPs for deer and 220 grain FPs for anything needing greater penetration.
Greene county NY. A few years back a bear was taken at around 700lbs. last season a bear was taken the hit the scale at 580lbs. The bear population has gotten so large that the state opened a new early September rifle season last year.
