One thing is, you don't want to have an expensive knife on you.
YOU WILL LOOSE IT !!!!
Either by someone taking it, leaving it on scene, it falling out of your pocket, etc., knives will end up missing.
The big "rage" now-a-days are these ....
http://www.rescuetees.com/Rescue_Knives_s/60.htm
They are inexpensive and can do the job and if you loose it (AND YOU WILL) you're not out lots of $$$$.
There is a hard point on one end for breaking windows (it does work), there is a slot with razor blade for cutting seat belts (and those bear drinking bracelets you were to show you are of age)... and it does work, and then there is the blade itself, a straight edge and a serrated edge, roughly about 4 1/2 to 5 inches in length.
You do get what you pay for. I have 4 of them currently. One is in my crash bag in my truck. One is in my back-pack that I carry to school. One is in my pocket that is my EDC. The last one was gift from my brother sent from Germany. That one is not the best, so I keep it in my top dresser drawer as a gift for which it was intended to be.
One cost me $60.00, and the other two about twenty.
If you want to get her the nice one, the $60.00 job ... here's the link.
http://www.sogknives.com/escape-hard...-serrated.html
Or you could just Bing (or google) for rescue knives with seat belt cutters and shop from there.