Estelle's smart. I feel like there's this misconception in the community that she's a dumb noble with zero intelligence.
She's definitely presented that way at the start of the game, which is why I couldn't stand her at first, but there's definitely a lot more to her than initial impressions and even the early scenes show off more than you'd think, if you know what to look for.
That said, the whole thing with the vase was a bit weird, given her training.