I would talk to her mom and ask if this is normal behavious and discuss a way to curb it. You can't have a little one disrupting your other kids. She needs to adjust to the daycare, and yes, she's testing you, but this is the time that you NEED to remain consistant and you and mom and dad need to construct a plan to make the trasition easier for everyone.
I'm sorry you have to go through that. I know how rought it is. Good luck!