we have no idea how vanya knows russian (i mean, i guess. do we have any?), since she was adopted as a baby, so I was thinking..
maybe 13 year old vanya felt so lonely she started investigating her past. she was crying at 3 AM after spending the day watching her siblings train, and leafed through newspapers and magazines looking for news from the day she was born.
vanya found out she was russian. she idealized a biological family that loved her, learnt everything about russia and even learnt russian cause honestly she was this desperate. she started speaking russian and only russian, taking pleasure in her siblings' confused looks and feeling revenged even though they didn't care..
except that they did care. they cared so much they came together, connected the dots and learned russian (well let's say they tried to). one day, they surprised her by answering her in russian. they intended to make her feel seen and included, but guess what, she's an unhealthy INFP.
being russian was HER thing, the closest thing to an identity she had, and they stole it. they stole her identity.
she started crying and ran to her room.
the hargreeves siblings stared at each other. five yelled he told them and left. diego and luther argued about whose fault it was. allison tried to break up the fight they started up. klaus and ben just stood sad, really sad, staring at the direction vanya had ran.
and they ended up just giving up including her.. as always.