(S1E7) There's no way at least one of them didn't die
Venera 7. I still find it hard to believe someone survived it but let's suppose someone did.
They lost a lot of oxygen when the spacecraft was being depressurized and later when incinerated. If there's someone alive in there, the best chances for them to not run out of air is if at least one of them died so they have one less body to consume oxygen.
If so, Chadha 100% survived because she is needed to keep the life-support system.
We need at least one pilot to make the spacecraft return to earth so the second slot it's either Sasha or Valya. The other one is probably dead.