Tom and Eric, she wears glasses and I actually brought that up with her dad the other day. He said she was tested about a year ago, and has been fine otherwise with them.
Another note, is that she loves playing catcher, and is one of 2-3 girls that can actually catch the ball when it's coming in. That makes me worry a little less about the vision issue, but it still could be the case, as she's squared with the ball while catching.
Do you know what she wears glasses for (farsighted, nearsighted, dominant eye etc)? This may give you an indication if any stance and positioning changes may help timing. I remember hearing about Kelly Kretschman going to an open stance when she discovered she had dominant eye last season and having a career year hitting as a result. Think David Ortiz did same thing.
One drill you may try to help get idea of starting earlier over is to use a volleyball or dodgeball for throwing BP (throw it pretty fast). Much easier to track and instant feedback on mis-hits, plus a 7 year old will think its funny to try and hit comebackers to nail you with it.
Try having her coil/load as the ball passes over the pitcher's head and think swing on every pitch.
Kinda like:
Best I could come up with without digging...