Wow, okay. First of all, she should definitely go to the doctor and describe any other symptoms. If she is experiencing pain, I can understand why you might think that it is the product of a tight skull.. otherwise, I don't know what you're talking about.
Insomnia can have many sources, but I think that the skull thing might be jumping to conclusions. One of the main sources of insomnia, or sleep disorder in general, is stress. If she is experience any symptoms of anxiety, this could definitely contribute to insomnia, and it can be a viscous cycle, worrying and not sleeping, and worry about not sleeping. I was diagnosed with an anxiety disorder a couple of years ago, and put on an anti-depressant. I took ambien to help me sleep for four months, but eventually I balanced out enough to sleep on my own.