Just a thought...
Is she using the correct sized strap? I know most brands usually have 2-3 different sized straps available for each head. I don't know if this would make a difference of not, but if she has small wrists (assuming), and she uses a larger bodied strap, then when she tightenedthe strap down to fither, it wouldn fit incorrectly, and in turn might be putting unusual pressure that is cause the pinching.

I don't know if this makes a difference or not, but thats what popped into my mind.