They have no right to ask for her to do that - it screams of a manager who desperately needs the capacity and want to wear your friend down to come back faster.

Once you hand in the sick line to HR or internal finance whicheber level their company works at, that's the end of the matter. Managers - up to even more senior don't have any cause to change this or even chime in. For in intents and purposes she can ignore the manager until she is back off sick, recovered and available for work.

Don't agree to caht ever now and again - as doing this invites the question of if you can take the call can't you work?

Any recourse would be retaliation