DD won't go to bed, once she's asleep she will stay there all night and this has only been happening for a few months now but when first going up she will get out of bed and come to talk to me every 3 seconds and that is literally. She can do it about 25 times.
I tried the supernanny advice of ignoring her, putting her in bed and leaving but she loves being picked up or me walking her back so she laughs and gets up again just so I will do it 
I've tried ignoring her completely but then she screams at 6mo DS to wake him up on purpose then I have to speak to her to beg her to stop
I put her to bed at the same time every day 7:30pm, it used to be 6:30pm but it was even worse at that time coz then she said she wasn't tired (due to the daylight).
She has a nightlight and a comforter, i have a routine of pj's, one story and bed.
The problem I think is coming from her DF's house, he lives with his parents and they all refuse to give her a bedtime at all. Could be 9-10pm. She stays there 2 nights every week and no matter what I say they categorically will not change what they do (they see it as me making demands)
What can I do because we are fighting every single night now