This sounds like a real ordeal for you and her. Parenting is a tough gig, isn’t it? I would suggest the following:
Connect before you correct - spend lots of time working on connecting well with her in a way that is meaningful to her. Lots of positive attention, play, put your own phone away and listen lots and lots. Don’t change anything until you are confident that you have a healthy connection. This is going to feel like hard work when she is having a tantrum, but keep the end goal in sight. It may eliminate some of the tantrums without any other steps needed.
Ensure that her basic needs are met. Sounds over simple but some kids don’t know when they are hungry/tired/thirsty so we have to anticipate and fulfil their needs so they aren’t being triggered by feeling uncomfortable.
Be confident that she isn’t neurodiverse before going any further. Read up on autism, ADHD and PDA. If it seems like she might be ND - get skilled support and read up on parenting an ND kid.
Start putting new boundaries in place one at a time. This is a process that will take time but you both need time to adjust and that’s OK. Talk to her before you implement anything new so she knows what to expect. “I’ve noticed that you are having difficulty with x and this needs to change. The next time y happens, I will do z.” Do not give any consequences without a warning because it doesn’t give her a chance to change her behaviour. If she does change her behaviour, thank her and give lots of meaningful praise and encouragement. If she doesn’t change her behaviour then it’s time to implement consequences. Sometimes the best consequence is a lack of your attention. Try and ensure that any consequence is related to what she is doing and she knows what it will be before the behaviour happens. Stick to it. Do not give in. Boundaries make children feel safe because they know where they stand. When you’ve cracked one issue, move onto the next.
As screaming is a problem, make sure that you aren’t raising your own voice to gain control otherwise you will look like a hypocrite when you want her to stop screaming.
Make sure that school knows what you are implementing at home so that it is backed up in the classroom and just in case she starts acting out at school when you make changes at home.