Micro Manager

I have a senior in my team who considers herself a manager, when she's not. She's just my senior. She will ping me 100 times in a day and delegate me more tasks before even before the first one is complete. She knows nothing about how work is done as she keeps delegating it to others. If I don't respond she keeps calling and she calls me in the middle of the night too. I have a really cool manager who doesn't ping me daily, will only ask for the deliverables on the deadline. I would have ignored my senior as she's not really the manager but she is the manager's pet. I have seen her delegate tasks to her seniors as well. It's been only a month since I have joined. Any advice on how do I deal with this? It's getting really frustrating.