Wow... that's next level pessimism.
I do think lowly of myself in some areas (socially, physically, etc.) from time to time but I never treat my assumptions (on how others think of me) with absolute certainty. The only way for Liselotte to be sure would be to actually talk to the prince about it, but even with that there's still the chance of him lying to her (unless she can read minds, she can never truly know how others think of her).
TL;DR, being certain about how others think of you is really, really hard to do without being biased.