Its sounds like you are doing all the best things, it will maybe just take time - I wouldn't point out what it is you are doing with the snacks, just ignore her and see what she does - maybe nothing, but after a few days with no pressure or attempts to feed her, she might just go for it. My eldest was not a good feeder, we used to get him distracted with a toy (mainly jigsaws) and shovel food in when he wasn't paying attention. In retrospect, it wasn't the right thing to do, although we did stop short of force feeding. he was a bit older than your grandaughter (about 2 and a half), when we just gave up and let him be. It only took only took about a day and a half for him to voluntarily get a spoon out the drawer and tuck into my husbands spicy beans on toast. We then realised that he liked spicy food and he has never looked back.
I hope it al works out for you, I can remember how stressful it can be, and they pick up on that as well which doesn't help.