Hi op, hope you've had a good night sleep and feel ready to take on the day!
My son is nearly 5 and awaiting an ASD assessment, he has some additional needs which means he's not safe to be left alone if awake at night (which unfortunately is often, although not as frequent as it used to be)
We have to have really consistent expectations and boundaries with him or it's just chaos. If things "slip" because we're all shattered, we've been ill, holidays etc we always need to take a big breath and re set/start again. It really does work.
He's not got a tablet or phone but does watch telly - proper programmes with a storyline, no YouTube and no telly after tea. Consistent so he knows.
He can be very stubborn - we make our lives easier by cutting stuff out so it's not available to be a battle. When he was 3 he got fixated on ice cream over the summer. Absolutely obsessed. So one day we said after the last one had gone, we weren't having it in the house. It's been almost 2 years since we've had it in our freezer! He has one when we're out and about or at my parents but he knows it's not at home so it's not a battle.
Just set boundaries you're comfortable with and stick to them - no telly after tea, this bowl of cheese for your pasta but once it's gone it's gone. If she only eats the cheese it's fine, but nothing else until supper.