Never had a lick of problems with it, and I had fired all sorts of ammo through it...Good and bad...
If the cases aren't extracting or feeding properly,then it just sounds to me like an ammo problem...IMO, Sigs can be a little finicky when it comes to lack of cleaning and lubrication...I bnever went overboard on any lubrication of any firearm I have, but it was enough to keep things working withough any problems when Icarried this pistol before I was bit by the Glock-monster...
For you in might be a combination of things, gun needs a little TLC, and the limp wristing, while you say it cannot be a problem,it actually might....40 firearms are sometimes not very nice to the female of the species, my wife never liked the caliber, because it did have a bit of a bite when you shot it...So she got to be a lot better shooter with the 9mm and strangely enough, but not surprisingly with the .45...
Try someone else's pistol (unless your good on those as well) in one of those two calibers and see if she has the same problem...
I hate to sell my Sig, but a good friend needs a pistol, and I'm going to cut him a deal because he has demostrated his seriousness of purpose in learning all he can about guns and the law, and has developed a great mindset when it comes to self-defense in general...That Sig of mine is going to a good home, and it will serve him well...