Do I Report Her?

[CloseToTheEdge17]

DH's EXW recently got a council house, and she asked DH to write a letter stating that we share custody of their daughter so that she could get a 3 bed.

DSD(17) actually lives with us full time (she was supposed to be staying at her mum's a few nights a week), but she now rarely sees her mum and her mum is refusing to let her live there at all stating its too disruptive for her DS(7) (she's just split from his dad). She doesn't even have a bed for DSD to sleep in on the rare occasion she does stay the night.

Am I wrong in wanting to report her for lying to the council to get a bigger house? I'm so cross that she's lied on her housing application and has been given a 3 bed house yet refuses to let DSD live there!

Your poor DSD, did she get her hopes up as well about being able to stay there? That's pretty crap of ExW if she did, at least she's got a loving home with you guys.
As much as it's eating you up that she's lied , I'd leave her to it simply because I don't think the council will do anything. If I thought they would and someone who genuinely needs that property would get it then that would be different but I doubt it.
There will always be those who lie and cheat to get what they want with no regard for who they might be taking away from, and it's natural to feel it's completely unjust (it's not petty or jealous) but I do think it catches up with them eventually so don't let it make you miserable. You've got a good relationship with 17yr DSD, that's all that counts

I think the problem here is that ex wife is out partying and drinking while op is taking care of dh's and ex wife's daughter full time. Ex wife is also manipulating op's husband. I generally agree that keeping out of it entirely sounds nice but it is affecting op's life. The ex wife has involved op by dropping her daughter 24/7 at op's doorstep and by manipulating op's husband.