I wonder if her taking an anti-inflammatory, Advil or ibuprofen, about an hour before sex would help?
The other thing, and this is way out there, is if she's ever been involved in any sort of head/neck traumatizing accident (car accident, bad fall, whiplash) she may have some problems in the upper cervical region, particuarly with her hands going haywire like that. A good chiropractor, particularly if they have training in craniosacral therapy, may be able to straighten her out.