Flandre's first impulse is to also jump--then try and jump and plant herself between Feliks and whatever it was that made the noise. Then she remembers she's pretty much there already, and does her best to keep still, though her wings are still half bristled.

Partially because she was certain facial muscles didn't work the way they did in the film, partially because...she was at a bit of a loss as to where to put them. Feliks was in the way of where one of them normally folded up.

...maybe if she just draped the wing on his head, in place of her hand.