Marya arrives at the Rostovs, agitated and anxious to see her dying brother. As the Rostovs fuss and fawn with the formality of greeting, Natasha ("with light, impetuous, almost merry footsteps"!), comes to her rescue.
Dark and light, the two princesses bond in grief.
from page 463-464, volume 2 of original text
Pevear/Volokhonsky translation page 977-978