I don't _think_ there is a "return spring" that holds the kickstarter inwards, but instead a ball detente or something similar that clicks in when the starter arm is in the inboard position. You can hear it "click" when you flip it in or out. I could be wrong though and it might be a combination of the two (a coil spring and ball detente)
I've ridden a KDX with the short kickstarter (I think it was a Fredette) and it was both harder and easier :)
Harder, because the shorter length meant you didn't have the same mechanical advantage when kicking it over. For myself, it was still pretty easy to kick over (KDX's are easy to kick start in general), but if your girlfriend was on the ragged edge of being able to start it, the shorter arm might push it into the realm of "pretty darn tough"
Easier, because the compact arm is easier to get your foot on top of, especially if you are shorter, or if the bike is in a tight spot or on uneven terrain...
It took me a little while to get used to it compared to the standard kick lever (I always wanted to give it that same kick "motion" I use on the standard and it felt awkward) but after just a little bit of time, I grew to like how it worked. and after going back to my own KDX with the standard kick starter, it felt like I could kick start it with my forehead LoL!
Good Luck!
Feanor