So, number three then.
From the start she seemed utterly affronted that I refused to morph into an exact clone of her two biological daughters (adults and left home by the time I arrived)
By that I mean I always felt I was required to be tall, slim, effortlessly elegant, easily tanned in summer, able to make friends at the drop of a hat and academically clever.
Whereas my natural set up was and is short, pasty white which refuses to tan, leanings towards the ginger in hair colour, bit shy until I get to know someone, not thick but no genius either.
My weight was an issue almost from day one of my arrival - constant comments and 'conferences' with her other daughters as to what could be done about my 'fatness' - family members instructed to keep calorific foods out of my reach at the dinner table, literally bags of carrots being left out for me as an 'acceptable' food.
When I look at photo's of myself from back then there really is NOTHING wrong with me - ok, I always had odd hair and a slightly chubby looking face but I was alright - not over nor underweight and always active (farm life and it's chores made sure of that coupled with almost daily sports activities)
Both foster parents were very high up in the local sports club and any spare time was and is spent either taking part in or organising sporting events.
I tried so so hard to fit in, to be a success at the things that were important to that family but was never able to make the grade. Any sport achievements were shot down with 'oh yes, but so and so child does it so much better than you and twice as fast' - every single time 
She would go into my room often and take out items of particular sentimental value/pleasure to me and hide them.
The rest of the family would then be informed of my latest carelessness and I'd be shouted at for losing these things and not respecting what was given to me.
Eventually I turned detective since I knew I hadn't 'lost' these items and sure enough, she'd stashed them on the top shelf of her wardrobe. Couldn't say anything of course as that would have created another row about my daring to snoop.