The 27s recoil spring SHOULD be stiffer than the 23 or 22 because it has the same recoil pressure distributed over less slide weight and travel. But the real problem with racking a Glock is the wonderfully slick finish. In my experience the issue is trying to get a firm enough grip on the slide to pull it back without it sliding through the hand. Have her try it a few times and then wet her hands and pat them dry and try again. If the second time is easier it's because the skin has more grip when slightly damp. It makes it much easier. The solution is either get a $30 "slide racker" or add either some type of grip/friction tape to the slide or have the thing re-finished or sprayed with a friction adding finish. I'm thinking of Rhino Liner in the slide serrations personally. LOL!