You can get perfectly good legal advice from AB, if you want it.
I agree, Peter, but this has been going on for 4 weeks - that is not a normal period for sorting out such issues.
She should write to the employer now and get it to them prior to their meeting on Tuesday. She should state that she is fit, willing and able to come to work, that her doctor has signed her off as fit for work, and then state that she proposes to report to work normally on Wednesday morning. That forces the ball into the employer's court.
Writing now forces the employer to at least focus their minds at the Tuesday meeting.
Then turn up on Wednesday morning as normal, report to her normal manager and see what happens.
What the employer will have to do then is suspend her (with pay) if they decline to allow her to work and send her home again.
I agree it is possible that the employer wants to dismiss her 'on the cheap'. By doing this they are hoping she will just go away.
At the very least, they have to go through a fair process of considering her capability (probably capability, rather one of the other possible fair reasons for dismissal), and give her notice (at least 10 weeks - maybe more if defined as longer in her contract) before fair dismissal might be possible.
By all means try and get 30 minutes free from a lawyer who deals with such matters.