I’m not sure if my comments will be particularly helpful, but I wanted to give a slightly different perspective.
I was selling my house due to divorce, I’d left him due to DA and so he was still living in the house whilst I was sofa surfing and living out of boxes, as was our DD. I think the fact she didn’t have a “proper” bed was a bargaining chip to convince me to go back home tbh. I used to go round and clean/tidy before viewings because he didn’t, he used to do things like not even bother to empty the cat litter tray and leave dirty casserole dishes in the oven that had started to go mouldy.
When the house sold he gave up even more (he’d moved his new girlfriend in at this point and I often wondered what the hell she thought of everything). When I was going round to start packing my things there’d be random bad “surprises” like the toilet bowl cracked, the kitchen sink blocked, or damp in the bathroom so he’d obviously not bothered to turn the extractor fan on. The garden was a jungle, I paid a gardener a couple of times when it was still for sale to just try and make it look decent. And he practically banned me from the house towards the end because I was a “vile, toxic woman and he was so much better without me and he hoped one day I looked in the mirror and realised what I’d thrown away”.
I was honestly petrified my buyers were going to pull out, and I sent them a message after apologising because I couldn’t believe how dirty it was on moving day. I posted a thread on here at the time because I was even off work with the stress of it because he just didn’t seem to want to pack, and I wasn’t welcome in the house, it was one of the worst times of my life. Either I did something really good in a past life to pull it off, or they did something really bad in a past life to deserve it haha, but they got a bargain. It’s an absolute tragedy really, because the house was at one point gorgeous, when the estate agent valued it she said it had a very “unloved” feeling to it.
I’m not saying you HAVE to go through with it, but if it’s mainly that it’s dirty I’d probably just hire a cleaner to do a deep clean. And I just kinda wanted to say people are weird, is she purposely not cleaning anything because she doesn’t want to move out and it’s rebellion against her ex?