Controversial thought - SD has a home, and her own room, at her mum's house. Where she spends 86% of her time per month, which is her choice.
And which is now financially facilitated by her SM.
She stays over at her DF's and SM's house for 2-4 days per month (max 14% of time per mth), where she currently has sole use of a bedroom. She doesn't leave much stuff there.
I'd be willing to bet she doesn't look on it as 'home'.
I'd bet she refers to it as 'staying at her dad's place'.
But due to changing health and financial circumstances, things have to change. She will still get to stay in a room that no-one else sleeps in, that's bigger than her step brother's, that she can decorate to her taste.
No, she didn't choose to be born, for her parents to split up, for her mum to remarry, for her mum to have 2 more kids who also have SEN, for her dad to have cancer etc etc.
Her stepbrother didn't choose to be part of a blended family either.
Her dad didn't choose to get cancer.
Her SM didn't choose to be the main breadwinner.
But life happens, circumstances change, and compromises have to be made. 🤷♀️
A desk in the room you sleep in 14% of the time is really not a big deal.