Well, don't forget that it is a medical condition, that it's not your fault (or hers), but also that it's not a life sentence. I know lots of people who have beaten it, so it is possible.
A study has shown that an amino acid called N-Acetyle Cysteine (aka NAC) can help reduce the urges to pull. In the clinical trial, 51% reported a reduction in their urges. I take 600mg of NAC a day, and it really helps me. You can get it from health food shops, or Amazon:
http://www.amazon.co.uk/Swanson-Ace...EJEO/ref=sr_1_1?ie=UTF8&qid=1301610494&sr=8-1
This is the one I use, which is also the cheapest, and the brand they used in the original trials. It doesn't help everyone, but it's worth a try. As it's a food supplement, you should have no problems taking it, but it's important that you take twice as much vitamin C as NAC (i.e. 1,200mg vitamin C for every 600mg NAC), to counteract any risk of kidney stones. It's a very rare side effect, and the vitamin C negates any risk.
Other than NAC, the best thing you can do is create a barrier to stop yourself pulling. Obviously hats and gloves, etc, but also try putting plasters/band aids over your thumbnails, which prevents you getting a grip on the hair. And wear a jangly bracelet (I'm assuming you're female) so that you hear and notice when you're pulling, so you have a chance to stop yourself.
There are lots of other little things you can do, but these are the best and most helpful. If you can get yourself referred for Cognitive Behaviour Therapy, it's worth a shot, as it is usually very successful in treating trichotillomania.
Mim