I'm sorry, but "standard English"? That one literally made me LOL! I was born and raised in Houston, so I suppose I've been learning Texas English (our accent isn't really the typical southern drawl) all of these years.
The stereotypes that are still around astound me, and they're here, too. Hopefully your girlfriend's mother is just trying to keep her close.
Just to give you a bit of perspective, many of the schools in Houston and the surrounding areas do their clinicals in the medical center here (many of them are located there, too!). People fly from not only around the country, but around the world, to receive care at some of the hospitals that make up the medical center. My point? If the south is that bad, why do we have such a great medical center here? There will be good and bad no matter where you train.
Good luck with your decision!