@GloriaSicTransitMundi
The girlfriend has had the benefit of living totally free (housing, food, clothes, toiletries, private dentist, medical insurance, car, holidays, plus every other expense) for 18 years so far and hopefully many more for the duration of my DF's life. She doesn't cook and the cleaner cleans, so she's a holiday companion really, rather than a home maker.
At the end of the day, it's her issue, not mine, that she a) never bought a property of her own and b) never had any sort of job of her own. She's never worked, so I'm not even sure how she'd qualify for the full state pension.
Also, 3 of her 4 children live either free or for a substantially reduced rent in properties owned by my DF.
They'll have the length of probate to vacate, so 6-12 months or longer.
100% though I expect a legal battle on her part to remain in the house!! My counter argument is that the funds from my late DM's business bought the properties, the girlfriend hasn't financially contributed to the running of the main house, she hasn't physically maintained the house and further, she hasn't done a days work in the business. She's benefited 100% and contributed 0%.
In any case, she has no money to maintain the house and land, so I'm hopeful no court would determine that she has a lifetime interest, as I'd end up with a dilapidated property that diminishes in value.
Appreciate that this is a different case to the OP, who is paying half for the running of that house and also doing the majority of housekeeping.