Thanks you all the great advice.
Although she wasn't able to shoot the Ruger she really liked the way the compact stock felt. The question is what to get. Would it be ridiculous to get a standard American with a 22" barrel and put a compact stock on it? I'm thinking that especially in .243 the 18" barrel would increase blast and cut performance. What would be better full power .243 loads or reduced 7mm-08 loads?
A Standard American with a Compact stock is what I was planning on getting for my 8yo son, whose not much smaller than your girlfriend. I figured that if after using it awhile and she wanted a shorter barrel that it would be easier to trim the 22" than to have to do a whole rebarrel on the 18".
