How to deal with this?

[FosterGuardian]

I am fostering my nieces and I am finding it very difficult with the youngest.
She went against my rules about social media safety so I took her phone away. She has ignored me for over a week and only spoken to me extremely rudely when she has spoken.
I am really struggling as it has been a week and I feel like I am getting nowhere.
I am getting no support from anyone around me and I am close to just giving in and giving her phone back
help I need advice

How old?

How old? Did you give her a timescale or means of getting her phone back? You can’t just take it away forever.

What was the rule she broke? Have you set up parental controls on her phone so she can’t access/download things you don’t approve of?

Yes what age is she and what did she do?

She is 12 turning 13, she has been sending messages to a person she has previously been told not to message due to inappropriate conversations (sexual).
I agreed if she was to share her password and we deleted the particular app she could have her phone back but she is very stubborn and not giving in
I am trying to set up the parental controls but can’t do that without passwords.
(the person who was caring for her previously set up the phone without them)

Ohhh wow. So the boundary you have set is 100% appropriate and under no circumstances should you give that child her phone back without you being given the passwords and setting up parental controls. The poor kid, this will all be so hard for her as she hasn’t had boundaries like this before, but honestly, deep down I bet there will be a part of her that knows you are doing this to protect her and will feel cared for. Maybe not right now when she’s angry and she may never express it, but you are doing the right thing. It’s hard facing their anger and pushback, but you are doing a perfect job.

Would it be possible to essentially wipe her phone and start again from scratch setting it up properly with parental controls?