So about an hour ago i went to shower while he watched the baby and the big sister ... he changes…

So about an hour ago i went to shower while he watched the baby and the big sister ... he changes the diaper and goes to throw it away .. tell me why my 3 year old daughter decides to get her pink two step stool from the bathroom while i shower and goes to the changing table of the playpen to put a penny into her 7 week old brothers mouth !!!

I can’t even shower or do anything without this little girl doing something to the baby !!

I am so scared to do anything ! Like is this just a phase ? Is she just a little jealous ? Every time i have him in the stroller and she tries to peek into the stroller and i look away for two seconds , she puts his blanket over his face . I try to explain to her that he can suffocate but she thinks it’s a joke ... has anyone ever dealt with this ??