The problem with most of these trailers is that they were supposed to be temporary and many places are trying to make them permanent structures. They leak, have rodent issues, mold issues, etc. It's unfortunate she has to work in one of them.
There was a moldy smell in a portable at my kids school this year. The teacher, tired of waiting, marched her entire class onto the gymnasium stage and set up class right there and refused to budge.