Please guide me with the changes happening with my preteen

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DD1 is 12. we are having lots of clashes like she is not listening sometimes or being on the phone all the time especially facetime and i feel like i don't have any privacy etc. No boyfriend just general facetime with school friends or cousins. No issues at school , she is considered as polite , kind and well- behaved child from school report. No issues academically , homework completes on time.
The way she replies back always on aggressive way with her siblings and myself. I don't know whether I am not dealing with it correctly. I do check her phone regularly and she doesn't like it. But we have been told by school to check this regularly.
Please guide me how can i help her / support her so that we can have a better relationship. I feel sometimes I might come across as controlling in terms of phone/ screen time. I feel sad

bump

It's not unusual at this age to push back against your parents.
Checking her phone and internet use is actually really important but I framed this with my DD that I would generally respect her privacy but she had to understand that if I had concerns then I would check her phone. No arguments. She wasn't allowed to change her pin without telling me the code.
I was very strict around things like apps/social media - she wasn't allowed accounts on anything except WhatsApp and that was for messaging only and I had to know who she was friends with.
No YouTube channels no insta no tiktok. No phones in bedroom overnight.
She was allowed quite a lot of screen time as long as homework etc was done..
I have relaxed the rules as she has got older and demonstrated that she can use the internet without harming or frightening herself..
You have to have a thick skin to the comparisons with their peers. But I think giving her a pathway to greater freedom and autonomy isn't a bad idea. Part of that is not sulking about age appropriate restrictions.
I've always had pretty high expectations around being spoken to politely - rudeness isn't ok. I'd ask if she would be happy being spoken to the same way next time she's rude.
But also remember this is the same person you know and love, they're just growing up. Adjust also how you speak to them and think about ways to allow freedom and independence. Show an interest in what she does and likes and make sure she knows you will always have her back.

Thank you @Beamur . This is really helpful