Mariel (on the left) has Weird Luck.
Angelica (on the right) doesn't.
In that first panel, Angelica is understandably surprised by the falling-through-the-floor incident she just witnessed. After all, that sort of thing doesn't happen every day.
In Mariel's experience, on the other hand, that sort of thing happens all the time. The only reason she's so surprised is that for once it didn't happen to her.