Kathy,
Yes, please do look for another trainer.
Besides the issue of possible damage to your pup's trachea, I agree with you that this trainer's method will likely make things worse rather than better. Using this method, she will not only associate strangers with something to fear, she'll also associate them with pain. AND, by hurting her whenever she growls, she's being taught not to growl so then what have you got? A dog who bites without warning.
If it were me, I'd do three things:
1) Look for a new trainer - a
positive trainer this time.
2) I'd follow the advice from windsor'smom and socialize her more. Put lots of yummy treats in your pocket. Make the appearance of a stranger = Treat Time For Molly. The goal here is to do this when the stranger first appears but before Molly has a chance to react. You don't want to give her treats once she has started misbehaving. If she's already acting up, you've missed your chance. Ignore her, move on, look for another chance, and try to shovel in those treats faster.
3) I think following the NILIF program would be helpful for Molly. I'll post it below.
Good Luck!