Is it legal for the company my Mom works for to fire her while she is injured?

My Mom got injured on the job over a year ago. She had multiple compacted vertebrae and has been going numb in one of her arms slowly. She was on workman's comp. and going to doctors appointments and physical therapy. They have not paid any of her doctors bills, like they had originally agreed, and cut off her insurance just recently. Her doctor and multiple doctors said it was necessary to get a operation in order for her to be able to go back to work, but they refused to let her get it. (They as in the insurance company through her work and a IME they had hired.) Instead they sent her to more physical therapy, which they also said they would pay for but haven't. She, despite all this, was hoping to go back to work, she loved her job.Now just today they sent her a check. They haven't sent her one in months, from what it seems though is it is a farewell, you are fired, check. It has multiple charges and other things marked on it to where it is pretty much nothing. She is still working with W.C. and a lawyer on this injury issue. Is it legal for them to fire her while she is still going through this? And is it possible they may never pay the medical bills and compensation they had originally agreed to? Oh yeah, and it took three months for them to even give her the first check they were supposed to. This is in Oregon.