How will you have Imogen tip you?

With some community service

As much as you would enjoy the favours of this delectable damsel (and fully intend to do so when it's her turn to be your maid in the future), you don't want to undo all the good work you've put in today, so instead you decide to take the opportunity to enhance your relationship with your neighbours.

"When you have the opportunity, Imogen, go to the street where I live and knock on my neighbours' doors, two or three on each side. Ask them whether there's anything you can do for them. Tell them I sent you and why."

"Oh!" Imogen seems shocked by the task, blushing in shame. "D-do you mean I should let them know the reason you needed to punish me?"

"Exactly. Tell them what a silly girl you've been."

"Yes, Professor. Thank-you, Professor."

"Alright, go on now, I'll see you next week."

With a final thank-you, the slim brunette fixes her clothes, gathers her things and exits just as gracefully as she entered, although you suspect rather more painfully.