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If she doesn't take hints just tell her bluntly "sorry I'm really busy, head home and we can catch up later"... she doesn't sound easily offended.
When she arrives say thank goodness you are here and get her to clean your house. Win win. She gets company and you get a free cleaner.
Keep a handbag & some lippy by the front door. When she knocks on your door for a visit ..... say "sorry, I was just on my way out for an appt" & drive around the block, (add extra stuff like, I'll be out all day, if you want). Do this a few times, then try, I'm super busy most weeks ..... Wednesday's are my best days for a catch up / coffee.
Maybe she is lonely why dont you ask her what else she does? Or what her plans are for the next few days and work in for the next few days you will be busy so wont be able to catch up. I think its worth being gentle you maybe her only "friend".
My SIL used to do this when our babies were little. She'd rock up at 9am and leave at 4pm. I felt obliged to sit and talk to her and I was too polite to say no. I started just doing my housework while she was there and it didn't faze her one bit. We moved 45 minutes away which was a bit extreme but worked well.
This was so normal 30 years ago 😂. Not trying to say you shouldn't be annoyed because I would be too, but these visitors that just pop in everyday were a regular thing when I was a kid. Its the difference working mums has made. I'm not sure what you can do besides just say I have heaps to do I don't want to be rude but I will text you when you can come and visit. Or maybe its her child that is pushing the visits? And she is tagging along because she does not want to just lump her child with you? Maybe she is lonely?