So... let's get to some points:
It's not like the MC is abusing, deceiving and taking advantage of a totally innocent and inexperienced person (like a Lira, for example)...
Tiffany has been acting like a "bratty" since day 1. Not only with the MC, but also with the most dominant character on the ship, Camila. So, from my point of view, it's clear that what Tiffany is looking for is NOT a "boyfriend" or "pure love" (like an Ariel, for example)... What Tiffany is looking for is to be disciplined, to be dominated, in a way, to the point of being humiliated. It's actually a more normal fetish than many people imagine.
I understand that many people consider Tiffany their favorite and, if the game offered the option, they would follow her path alone (although that's not what the game is about). We don't know much about Tiffany's past. This preference of hers may have an explanation in the past (daddy issues?) or it may simply be a personal preference. You need to understand that this exists. Like it or not.
At no point was it shown that Tiffany was deeply sad and/or feeling humiliated by everything that happened and how it happened. On the contrary. From what was shown, it seems that she was satisfied with everything, as if she had achieved her goal, something like "finally the MC reacted and did what I wanted/needed."