I agree with the above, and also am wondering if the dad has a problem with it. I think seperate sleeping is always best for all concerned (my opinion) but perhaps this is his cuddle time with her as well and that is why he is continuing it. Then you have a little different situation. You don't want to fight over his daughter. Good luck.
I can understand where you are coming from and it would be a good idea if he still cuddles his daughter, and stays in her room to read her a story ,then leaves her, she will not like it but she will get used to it, if he doesnt want to do this, he should tell her he will lay and cuddle her for a few mins then he has to go to his own room. Key is consistancy , if he doesnt he is sending her mixed messages and she will know he will give way.Same in the night he sends her or takes her back to her own room tucks her in then leaves the room. It will become a habit and after a few days all will be well.How often does she visit as that makes a differance , if she only sees her Dad every so often it would make her more needy for his time, and you can afford her that cant you ...