the house work needs to get done but at this point there is no way of this happening unless she takes it upon herself, which is extremely unlikely.
This is going to sound weird, but, why does the housework need to get done?
She chooses to live in her house like this. She apparently agrees "something" needs to be done. But she is never going to do it herself if you intermittently help her. I know her house is likely not ideal, and likely is reaching a rather gross level in some places if not all, but just like you can't control her, you can't make her control her space.
Does it need to get done because it bothers YOU to be over? Because it makes you uncomfortable? I realize the hazards of a mess, please keep reading, but we all have to work on removing our desires for what we want as normal from what our pwBPD can do and are willing to do, and see where we can meet and agree with them before any progress is made.
H is not good at keeping up with housework. Since we live together, this affects me directly, and upset my calm, and I like a relatively tidy place. He would be fine washing dishes only as he needs them unless company was coming over. He can let the trash pile up into needing 2-3 bags before it dawns on him to take it out, and I bet he has never paid attention to the days the truck actually comes for it. But since we share a space full time, I clean the house, I do pretty much all chores as I am physically able all myself, because I want it done, I feel better in a clean house, and so does he overall, but it's my neatness-needs that drive me to do it. If I can choose between a nice morning and a fight over doing dishes, I'd much rather do the dishes. I lost any drive to nag about it, engage in fights about it, and try to not get defensive when illness or long work hours prevent me from cleaning and he gets cranky it's not done.
Some of this is simply due to the fact some people are neater than others. In most couples, one person is "the slob" and one is tidier. In society, we often expect the woman to be more tidy, but this is not true at all - I know men who are really really neat freaks and vacuum daily.
Add to this his mother is a hoarder. She hoards things, trash, and tries to hoard animals. She is both overwhelmed by her mess, and also seems overwhelmed by open space to the point she must put something, anything, a box full of 10-year-old paperwork into any open space. This means for her, it's natural to have only a one-foot walkway in any room (unsafe for two elderly people who can barely walk).
H gets overwhelmed there. He hates the mess, but also feel powerless for two reasons - it's a lot of small decisions to make as you sift through things to clean (I can make these pretty quickly for MOST items - trash, but he got a paralysis about such things from his mom). Also, his mom freaks out that her legacy is being destroyed, and she does not realize or care that her legacy is under a pile of old magazines, bills, and cat vomit, and she is ruining all she cares about by leaving it in piles on the floor, on tables, on counters, rather than throwing away trash and putting away useful things. When she DOES try to clean, she reads every single damn piece of junk mail to be sure it does not need to be shredded (H also does this) and it's not got some things she may want to save.
In order to visit, I have learned to simply move things where she can see them, that I have not thrown them out (some I DO throw out - expired, gross food, yes, u the trash - hidden under paper towels so I won't get yelled at for being wasteful). We have a limit as to how long we can stay without feeling a need to alter the enviroment to a level for OUR comfort that will cause her to fight us.
Anyway - I tried mentioning mess, arguing about mess, making statements about mess. What I have found with H is that words don't go as far as actions and examples. He sees me get up for work on days I feel less than well - he is less likely to think it's okay to stay in. He sees me folding my laundry, 1 in 5 times, he will start to fold his. He sees me doing dishes, he might go put DVDs away. It may not be much, but it's something.
So at what level is your GF's mess? How have you mentioned it? How do you go about cleaning when you are there? Have you made it clear it makes you not want to be there? It makes you not want to come over/eat/sleep in a messy palce? That bugs are drawn to certain messes and things like paper and cardboard boxes? Does she come from a family of hoarders? Is she overwhelmed by losing stuff? Is she overwhelmed by how much mess there is? Is it just diry dishes and unfolded clothes,or is it even worse, like piles and piles of things all over where you can't even sit? How much can you clean before she freaks out? Or does she? Is it the act of cleaning and the poor executive control that comes with taking care of yourself perventing her? Or is it an attachement to things that makes it hard? Both?