Her acting is abysmal! Worse than her singing, which is weak as hell.
I’m pretty sure the whole point of Liesl in that song, at least in the movie, is that she’s playing along with what Rolf says... she’s trying to get him to kiss her. She doesn’t genuinely feel scared at a world of men, she’s excited about the future, but she’s acting demure and like she needs Rolf to guide her.
So, Gabby’s interpretation is all wrong. She’s making facial expressions that are literal (and poor) interpretations of the words, then smiling manically, making Liesl seem insane. She’s playing Liesl as the clingiest 16-year old virgin (who will probably save your number in her phone with an engagement ring emoji next to it).
duck’s sake. Such a musical theatre nerd, though.