If she has returned to her previous role, ie same job title/description, there is no probationary period – she already had that when she first took that position.
As far as the management meeting is concerned, if this is the entire management team then it is a reasonable request and you should endeavour to accommodate it. If you definitely can’t then they have to show compassion.
For what it is worth, I have been in hospitality for 12 years with companies big and small, where front line management haven’t a clue about HR. My last job we had a management meeting every Monday at 3pm, so someone would have to come in on their day off and sometimes we wouldn’t have full attendance due to prior commitments. There was always cake, so no-one minded.