Yes, it may well have nipped her a bit, and maybe that's why she's a little wary now (in case it happens again).
But she will get over this once you've clocked up a few 'normal' insulin shots. Cats are very forgiving.
I actually have a different shot technique to many people, and I wonder if it might work for you.
I pull up some loose skin between my fingers and thumb (rather as is shown in the photo below (but not so much skin as this!))
And then (
unlike the photo below) I inject almost directly downwards into the skin that I'm holding, midway between my fingers and thumb.
I never set out to give shots like this, it just sort of evolved over the years. But I have found that by using this method it's nigh impossible to accidentally jab the muscle, because the skin you're holding between fingers and thumb is 'deeper' than the depth of the needle. ...Just wondering if something like this might work for you..?