Recently, my line manager was asked to resign from her post and take up duties in my team. This was effectively a demotion. 

I am the team lead, which has left me in a tricky position. My now-ex-manager is not following the staff rota (shift schedule). I’ve noticed for a couple of days now, she’s not turning up for her shifts and is doing other work behind the scenes and getting other colleagues (who were on rota to be behind the scenes) to go out and work with the team.

I had discussed her hours with her before adding her into the rota. Arguably the work is mostly still getting done, but she’s creating a situation where some things could slip through the net and certainly where the staff who are under the most pressure are not getting the time away for background work that they need to renew their energies.

A couple of weeks ago, this was my manager. There’s been an unpleasant background to her being pushed into resigning her management job, so I feel bad for her. However she was not a good manager, and I’m concerned that my organised system is now going to be affected by her "interference." 

How can I effectively manage this person without hurting them more and not making myself ineffective?