I suspect it depends on the cause of her problem? My DD has made tremendous progress with her grip and her handwriting, she is a little younger (we started work at just before 6, which was the start of 1st grade for her, it's been a year and we have seen radical change). If she hasn't done a lot of writing I can't see that it's too late. When my DD had her evaluation a year ago the OTs opinion was that her current grip was due to being physically incapable of correct grip, but that by the time she was strong enough (if she ever was strong enough) that it would by THEN be too late to correct what would have eventually become habit/motor memory.

We use these grips:

http://www.thepencilgrip.com/dyn_prod.php?p=TPITPG-11401&k=27471

Previously we tried these and we loved them (until we tried the Jumbos):

http://www.thepencilgrip.com/dyn_prodlist.php?k=27440

For the first 6 months she was also using a custom designed brace from a hand specialist OT (mostly deals with injured adults). Now she just uses the grip. She is not expected to ever be able to produce volumes of hand writing though.