My wife said the .270 kicked too hard for her and she is a lot bigger than 85 pounds.
I shot my first 12 gauge at 12. Single shot that kicked like a mule. After that I have never had a problem shooting anything. Started hunting with my 30-06 auto at 15 and never looked back. The recoil of a .270 is about 7x that of a .223 according to
http://www.accuratereloading.com/recoil.html
A broke clavicle from not buring the gun in your shoulder is no joke.
I spoke to a lady in the office that uses managed recoil and she has seen it work in some autos but not others. Best bet is to try it out.