Have had a few previous threads, step daughter (she doesn't deserve the dear) has not seen dp for ten months now.
We had a few nasty texts from her mum a few weeks ago saying that stepdaughter had been emailing and we were ignoring.
Turned out sd was lying, hadn't emailed. So we got an email in the end, it was vile. She basically said that unless we give her a lie of expensive items ( think laptop, iPod etc) that she wouldn't talk to dp again.
So we both e,ailed back, we're very nice but firm. No we won't supply lots of expensive gadgets but we would love to take you out for lunch etc etc.
No reply, then had a call last week from sd's mum, sd was in the background. She accused dp of perving over sd's friends on Facebook 
Then had a phone all, clearly on speaker phone asking when she could collect the stuff on her list.........
I've called her this week and text her (nicely) to remind her it's fathers day and ask if it's easier for her if I get her a card and write in it.
Nothing. Not a single response.
Have no idea what to do now. She's 12 by the way.