Yep. The prince was affected by trance/charm magic (makes you wonder how is it so easy for royalty to be used?)
Initially in the threads, a few people claimed Leon was the ML (actually there's no definite proof just yet), recent spoilers mention the Prince has gotten interested with MC to the point he doesn't care if she isn't a light attribute user AND is hoping the other light user won't show herself. Also, MC gets to tell her family eventually the truth and they're PISSED at him.
Ah! I forgot to say, the other light user if it wasn't obvious enough, isn't a true light user. According to spoilers, she is actually attributeless but has an ability to steal attributes and possesses an infinity symbol/mark. She stole the light attribute from the last surviving light user (a half-elf who decided to live in a monastery) and the reason she targetted MC and the Prince is just as you'd expect, she fell "love at first sight" with the prince, even trying to stage an event where she inadvertedly saves him (but MC saves him instead), she's also being bullied because of her low rank and attributeless status.
And, the Prince's sister is one of MCs true friends, one of the few people who trusted her innocence even on the first timeline