Sister wants to be a boy

[mytypeonpaper]

So my sister is 10 she's always said she wants to be a boy (she has 2 sisters and a brother- there's a big almost 20 year age difference between the 2 of us)
when asked why she used to say because she wants short hair and to play with boy things and wear boy clothes, we told her that's fine and you can do that whilst still being a girl so we got her hair cut and she seemed happy. Now she's saying she wants to be a boy because she's born in the wrong body.

For context, her dad isn't really in her life and I feel like she's always trying to get him to notice her- it's heartbreaking.

She had a double barrelled last name and she told us a few weeks ago that she wants to drop part of her name and just keep her dads side.
she goes to church with my grandparents sporadically but recently she's saying she wants to be a born again Christian and be re baptised.

She text me and my siblings yesterday (from my mums phone) that she now wants to be a boy and can we all her X name.

She also wants to go and speak to the priest at her church but my mums reluctant to do so as it's a baptist church and she dosent think they'll be very understanding.

I've told my mum that she needs to book a doctors appointment to talk to a professional but I know we all need to sit down with her and discuss it properly.

Me and my family will support her 100% we are a very open family but part of me feels like she's just doing this to make her dad notice her and I really don't want her going into school saying she's got this new name and that she's a boy because I'm really worried she'll be bullied for it when it's not actually how she feels.

Can anyone give any advice on how to move forward with this I really don't know what to do and I don't want to do anything that will cause any damage to her mental health.
Thank you xx