<human>: Can you summarize the given text in a few sentences?

Hi everyone, firstly sorry for formatting yada yada, I'm on mobile!

A bit of backstory,  I have been almost no contact with my dad for a number of years and completely no contact with his partner for years now, they were both very emotionally abusive and I could fill /raisedbynarcissists with stories about my dad's partner. She has two children, one she had before my dad and one with him. I have contact with the older one online but we don't talk very much, I suspect they have both had their heads filled with lies about me. 

My half sister is now getting to the age where she has a bit more independence and is also just a bit older than I was when her mum came into my life, iv seen how she can destroy a child that age and while I feel she should be OK because she is her daughter,  I still worry about her. 

My half sister used to be the only good thing about staying at my dad's house, we were extremely close when she was a baby and toddler and I love her very much but I haven't really spent any time with her since she was 4 years old.

It is her birthday soon, I heard in passing from another family member that she has a phone. I was thinking I could write a small simple message in the card with my phone number, she's too young to hear my side of the story of course but I would love to start establishing a relationship with her again so that maybe one day she will understand that there is more to the story than the lies she has been fed.

I have no idea if this is appropriate at her age,  and I fear any backlash from her parents, I'm worried that this would enrage her mum and make her tell her even more lies about me.

I really have no idea how to handle this. Any thoughts or suggestions?
<bot>: I have had next to no contact with my half sister for years. She us getting old enough now to be somewhat independent and I would love to reestablish a relationship with her but I have no idea how