I started my daughter out with the 260 at 11 years old. She wanted to try my 300B with a brake when she was 14 and she hasn't let it go for the last 11 years.As bad as I hate muzzle brakes, I put one on my daughter's (14 at the build time) hunting rifle. A Win. Model 70, B&C stock in 30-06 pushing 165 grain Nosler Partitions pretty hard.
This was 30+ years a… I'd do the same today…..only substitute the Partitions with 150 to 165 Barnes TTSX's!
Her children started using it in their early mid teens! A lot of Whitetails have been taken with that rifle! memtb
To the OP, If it fits her OK, I'd let her shoot Grampas 270. But I'm nostalgic that way.