Help on what I should do

So, my husband I and our newborn are staying at my grandma's house while we move out to our own new place which is a month from now. Okay so everything was good except for this morning, my husband had gotten suspended from work but has to go talk to his manager before he goes to some conference but he had been slacking on going because he sleeps late and won't wake up in the morning however, he told me that today he was going for real so I set the alarms. Yesterday my grandma told me she felt like waking him up but she doesnt want to do it without my permission, I clearly said " no don't , he will get mad " . This morning I over heard her telling him to wake up and that hes been saying he's going to go but that he keeps letting the days pass by. I fell asleep after that and when I woke up he was mad and told me she threw water on his face and that it bothered him because she didnt have the right to do that and that not even his own parents had done that to him. Knowing him, hes not going to talk to her for a while. He told me before he left " you better tell her something or I will and its not going to be nice" . I'm stuck between letting them talk it out or telling her what she did was wrong . I don't want to be mean because she's helped us out a lot but I don't want to be living where there is tension especially now that my baby is born . What would you do ? And from the choices above what would you choose ? 

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