When a person gossips the way you have described it’s how that person is as a person.

It could be that she remains employed because she can speak another language. Yes it’s rude that she chooses to talk trash about you in front of you like that. I would not want any job that would include having to deal with that kind of person. A temp job gives you a chance to see that toxic before working at a place.

Sadly as you have been seeing there is a lot of toxic out there.