The same thing happened to me, one of many disappointments in the half-baked Switch port of this otherwise excellent game. Google "The Outer Worlds update 1.2 fixes a dreaded bug," and you'll get the whole (rather amusing) story behind the original bug, but as you've noticed that doesn't help us much. Unfortunately they seem to have ported an earlier version, so we'll have to wait for the Switch port to get updated - assuming they bother to do that. I actually noticed it soon enough to reload a previously saved file and complete her companion quests, which was totally worth it. Unfortunately the "Parvati died" flag was apparently still set somewhere, because after I'd beaten the game her ending card said she'd died while adventuring with me., even though she was standing right next to me when I finished the final level.
