Suzie:

At least your mom has pretty direct access to I-95. Don't know how long she has lived there, but evacuations from Hilton Head can be pretty messy affairs with basically one way out. NWS Charleston is saying forecast doesn't "bode well" for SE GA and Southern SC, but too early to tell.

Don't know what your circumstances are in terms of having time to get to your mom and then have it turn out to be unnecessary, but I recall stories of folks sitting on highway 278 for 8-10 hours, so my advice is obviously watch carefully, but if you can, err on the side of "too soon".

Bill