She may have had a wormer at the humane center. After the wormer is given you will still see worms for a little bit, only the worms will be dead, the body is just getting rid of them.

If she has live worms and it came out in her stool it would be tape worm. Tape worm is the only one that comes out. Other worms like hook worm stays inside. If you get a wormer make sure it is for all worms.

No reason to worry, she's in no danger.