I wonder if she is still rather in the ‘stunned’ stage of enjoying her new found wealth and doesn’t realise that she is becoming rather insufferable endlessly talking about her money. I can’t believe that she let you pay for lunch at the pub, it should have been her treat for you!
I would tell her straightforwardly, that you would love her to stay with you for the weekend but that you are too busy to have guests for longer than that though so if she would like to stay for longer, the B&B is still along the road. No need to fall out with her, although I’d be tempted to add “qnd you will be able to have a bath there!”
