I’m going through something similar, I have the kids living with me their mum moved out last year and is with someone else and is supposedly wanting her kids to live with her (only says this when it comes to court) yet she hasn’t called their school/attend any Christmas plays or parents evenings etc so it’s obvious she doesn’t want to put the effort in…
Although I’m in a minority being a dad with the kids, so many of my family and ftifrie have been through this stuff where the dad leaves fights tooth and nail through court to try and get access etc but then a year or two down the road meet someone else and their interest tapers off and they rarely actually see their kids despite making everything so expensive and traumatic with all the court stuff to start with.
If he is a decent guy he will just want to see his kids and not turn it into a battle over maintenance payments etc as in my experience the ones who do that are the ones who aren’t really thinking about the kids
But tell your friend she is doing a great job and things do get easier and as long as the kids are happy that really is all that matters whatever haooens