To be honest, when I stay there I just roll my sleeves up and start cleaning. Boil a kettle and mix the water half and half with cold to wash up, using loads of washing up liquid. Once you have a small area clean it's much easier to manage the rest of the week.
You start cleaning her house for her, pig!?
Maybe that's why she invites you over!
I'd be humiliated to let someone see my home in this state, let alone an extended stay, not that I'd tolerate it in the first place but still.
If we have visitors like later on today (someone popping over for a drink) the day before or day of the visit we have a proper deep clean of every room, get rid of any rubbish that has somehow outstayed it's welcome, fresh towels and dishes all done and everything dusted. I don't really care what others do with their homes when I visit (though if it was unsanitary I wouldn't go, I'd want to meet outside instead) but I just feel like it's a basic mark of respect.
She doesn't respect you, and worse still I bet she knows you won't be able to handle the filth and will feel too awkward to say you can't do it anymore, so she thinks you'll clean.
Is she even a friend? It's a big ask for a colleague, cheeky mare.