I disagree with the 'next time' argument.
The OP could have given her DD extra cheese along with praise for asking politely if she asked politely, and the comment that cheese is good for our bones.
She could still say no to sweets or staying up past midnight watching slasher movies. "I can't let you have sweets/ watch that movie," is an appropriate response, along with an acknowledgement that the DD may feel angry or disappointed or frustrated not to hear you say yes.
It would be important with this child to sit down with her when she's calm to talk about feelings, and to emphasise the fact that feeling angry or frustrated or disappointed or wanting something really badly are just feelings, and we can let them pass through us without losing control of ourselves. In the OP's shoes, I'd ask the DD how she feels when mum says no, and tell her whatever the feeling is, it's OK to feel that even if the feeling isnt a happy one. But I'd add that, "I can't let you think that screaming for something will result in getting it."
Sometimes encouraging politeness and giving a little takes the tension and the confrontational element out of the picture. Sometimes a little predictability and a little more flexibility about what's allowed can go a long way too - serve a bowl of cheese / bottle of ketchup, etc, along with dinner, make sure there's a water bottle by DD's bed, etc.
But I would definitely make sure that the phone was "lost" or "broken" and can't be replaced. Children should not have the experience of dissociating from their surroundings with a personal device. It is disastrous for their social skills and emotional development.
This is a child who has lost confidence in her parents' ability to be the family leaders thanks to the vicious circle they're all stuck in. Conversations about emotions need to be started by the parents, and the DD needs to be guided into recognizing and living with uncomfortable feelings no matter how loud or long she screams.