I think it could have been a setup. The Pharisees had tried to trap Jesus before. Simon, the Pharisee (Luke 7), invited Jesus to dinner with some of his Pharisee friends. He had already sent out one of his Pharisee assistants to pick up a woman of the street and bring her to his house. After Jesus arrived and the meal had begun, the women had been instructed to enter the dining room of the Simon's home - how else to explain her entrance into an unauthorized domain? She was a sinner, an outsider, and surely a fish out of water in a leading Pharisee's home. And so the trap was sprung. As she anoints Jesus feet which were not washed beforehand, and kisses them when Jesus had received no kiss of hospitality, and anoints his feet with expensive oil since no one has seen fit to anoint his head with fragrant oil - Simon and the others wait to see his reaction.
What will Jesus do? This sinner is hopelessly out of place. She is touching him, kissing him and wasting precious oil on his feet which are dirty and stink. She is a law breaker breaking laws. She is way out of the realm of social acceptability. There are so many reasons why she is the wrong person in the wrong place at the wrong time. Perfect trap.
Good time for a story. Two debtors one who owed a great deal and one who owed a much smaller amount. Neither could pay off the debt so the creditor cancels both debts small and large. It was possible but not likely. Hypothetically, which one would love the creditor more? Love? Strong word. Feel grateful to, or further indebted to, or just basically wondering how lucky could he be, all of the above more likely. Simon knows he has lost, see the sneer, and hear the sarcasm in his voice, well I suppose the one for whom the greater debt was canceled. (This was not a hard question.) The woman who was the trap was paid for her performance, perhaps. Or, she was performing because of a threat of a harsher punishment if she did not. She was surprised to learn her great debt had been canceled, even forgiven. She had touched and been touched by God in human flesh. In a place where she was more out of place than a sanctuary. She was a sinner who was used to being used by men even the religious. Here she was welcomed by true religion, her debt forgiven while Simon and friends were adding to theirs.
I can't say for sure if it happened just like this but it's plausible, isn't it. And the punchline is the same.