"I really enjoyed it last time we studied together"

I say.

Millie thinks a little bit, then says:

"Matt, this is what I worried about. I sucked your cock last week to prove to myself that I still got the ability to turn on young guys, and now I have proven that, so I am not planning to suck your cock again or anything else for that matter."

Millie let's her statement sink in for a while, then says:

"I really don't feel bad about it. Yes, I used you, but you got your cock sucked, so really you should feel like that guy at the end of that 'American Pie' movie."

I smile a small smile, that I hope looks sad and innocent looking, as I think about what to say.