Mal, I don't know what to say about that story. I don't know the person involved, but you have to admit that there is a lot of luck involved in a shot like that. I don't care if she is the greatest shot of all time, and she may very well be for all I know. The question for me isn't if this happened. I don't doubt it could happen, but surely you have to admit that this was her lucky day. I was thinking about trying to figure the drop on a .22 LR at that range but I wouldn't know where to start. As was already mentioned, I would think that you would certainly run out of scope elevation long before a range like that. And at a range like that, with the bullet dropping like a stone, extremly precise range and sight settings would be required. I bet at that range you could miss the whole squirrel if you range estimation was off by a few feet. Then you get into the potential accuracy of the rifle. A ground squirrel couldn't be more than a couple inches wide by maybe five inches tall ? If that ? We are talking about shooting better than MOA at 300 yards with a bone stock .22 autoloader.
Anyway, my hat is off to her. Skill, luck, whatever it makes a great story.