Correct. But, you have to have made enough choices to get Emma's naughty meter into the red. The vanilla porn option does nothing to add corruption. The other 2 choices put you on those paths...
There's only one, maybe two "non corruption" choices you can pick before selecting the vanilla porn option to get Emma's naughty meter into the red. One important one seems to be the choice to let her keep watching Martin or call out to her...
After MC talks to the father at breakfast, Emma will either send the MC a link to a video (cheating path), or she starts a vidoe call (all the other paths).
At least that's how the 20+ run throughs I've done testing paths play out...
I don't really want to do it...but if it becomes necessary, I'll do a choice by choice WT on how I get Emma on the cheating path...

The general instructions seem very clear, obvious.