[Mello2u]

CoalCracker
My question is, is this because the .40 was an SR40, not a SR40c, and therefore the recoil was less? Its basically the 40c but with a longer magazine, correct? So i figured the recoil was more manageable for her because maybe she had a larger grip to hold onto and it was just larger. If she shot the 9c and the 40c, maybe she would like the 9 better because maybe then the .40 will be too much in the C version

I have no personal experience with either the Ruger SR40 or SR40c.

Looking at Ruger's website it says the SR40 weighs 27.25 OZ. empty.
It says the SR40c weighs 23.40 OZ. empty.
It says the BSR40C & KSR40C and the KSR40 & BSR40 all can hold the same number (15 +1) of cartridges, so there would be no difference in weight gain due to loading the same amount of ammo.

KSR40 & BSR40 15+1
BSR40C & KSR40C 15+1
KSR40-10L & BSR40-10L 10+1
KSR40C-9L & BSR40C-9L 9+1

Depending upon the size of your girlfriend's hands she may or may not get more of her hand on the larger frame. These two factors mass (weight) and area of her hand experiencing recoil would be the primary factors in her perception of felt recoil.

If she has small hands that reduces the influence of a larger frame as her small hands would likely be filled with the smaller frame.

So go with her choice. It is hard to get blamed by your girlfriend for agreeing with your her. Her opinion matters more than ours. If it does not work out, you have an excuse to go to a gun store to shop some more.