When my kids were toddlers and would pull the 'you are the meanest mommy", I'd just agree with them. Usually surprises them and cuts off what they were going to continue with.
With the daycare, if she starts to balk, you could try explaining to her that the baby is too little to do stuff like that, but you can since you are bigger.
I agree with the help where they can rule. My older son would bring me burp clothes for the baby, give him back his pacifier. They were 22 months apart. The 2nd and 3rd are 3 years apart...and man, has that been tough at times. The youngest is 8 years younger, so she has a houseful of people telling her what to do
But she is very well-adjusted and she doesn't respond to things that the older one would...she still believes in Santa, but it's tough to pull anything over on her.
Hang in there...you always have her teens to look forward to