1997 VW brakes (not a GLS)....was driving and had to step hard on brakes due to truck veering into my lane and the brake went all the way to the floor. Up to that point brakes were fine. I only have 73000 miles on the car and my brakes and rotors were recently changed. The brake pedal does not sink to the floor when the car is off. I'm hoping its just the brake fluid. Can you help me? Sue

It is possible you have a blown line. Most vulnerable to this are the two front flexible lines that go to the front calipers. Next is the possibility of a blown seal, The seals are located in the master cylinder and the two front calipers and the two rear calipers or brake cylinders depending on wether you have disk or drum in the rear. If you can look under the car and find a wet spot usually drips down a tire, you will find the source of the leak. If you are losing fluid it has to go somewhere and as long as there is fluid in the resivor it will leak. The master cylinder, where you add fluid, has a front and a rear brake side to it therefore if you blow a line you have a backup.
If you look close at the resivor, using a flashlight, you should be able to see the two independent resivors and tell if one is deficiant .This will be an indication as to where there is a problem. If not you have a bad master cylinder which is malfunctioning.

Bad brake line somewhere or bad brake cylinders. The extreme braking you did to avoid the truck poped a weak brake line "most likely" or brake cylinder.