I also think they are just testing the boundaries...I would try to look at it from their stand point. Mom has been gone and now she’s back? Is she here to stay? Is she going to leave us again? Why should we trust her or listen to her...she hasn’t been a real mom?
Just continue to be a “real mom" now...give them love and reassurance, but give them boundaries and consequences. They will learn in time...mom loves us and she is in fact a good mom. I honestly think it’s up to you to stand your ground and not give in...Kids are tuff and can fight the good fight, and can bread a person down, but they want to feel safe and loved by you.