How do you progress with Betsy's training? I'm stuck at corruption 60 and I'm pretty sure that I've tried every possible interaction, so I've got no idea on how to progress to corruption 70.
Yes, indeed ... there is a rather complicated system with thresholds, which definitely needs to be simplified or painted in more detail.
In general, here is the exact information - if Betsy has a corruption of 60 and higher, then when she jerks off to Gaston under the table, then her corruption can be pumped up to 70.