My DD wet until she was about 10yo.
She was referred to the bedwetting clinic and given nasal spray and had bed alarms etc and would just sleep through them
She just stopped eventually in her own time. Bedwetting can be hereditary, caused by a fault somewhere along the piping, and also kicked off by feeling stressed.
In DDs case her father wet the bed and still does probably he certainly did when I was married to him! so was probably just hereditary, nothing else was found to be the problem anyway. Things are sooo much easier these days with night time pj pant things, there weren't these things around years ago when DD would have needed them.
Yes it's completely normal and not at all rare, it's just people don't tend to talk about it much for fear of embarrassing the child.
So get DP to take her to the GP for a check over and if nothing found a referral to clinic. Just cause the mum doesn't appear to want to do anything doesn't mean he should let it slide, he is her parent too and has an equal responsibility to get it sorted.
And I know how stressing and annoying it can get, to be having to do yet another load of washing etc... but really really try to just not react at all. She's only 7 which is still quite small to be dealing with someone being horrid to you for something that might well be totally out of her control.
MW at 1.30pm today, hope all is ok [worry]