Understandable
They've only lightly touched on this but, there's the underlying idea in the galaxy that "The Jedi will come to your planet and tell you your child is special and then take them away and you'll never see them again"
Reva was probably taken from her parents as a child in order to become a youngling, not even fully a padawan yet, only to be thrust right into Order 66 and be left with no family, no guidance, nothing.
If it's been 10 years since the Battle on Mustafar, so we know Reva has probably spent 10 years of being one of Vaders apprentices, being subjected to all manner of cruelty in order to become stronger and more powerful.
And with Anakins rage, he's probably blamed Obi-Won for everything he has lost
Man that Vader show that they eventually make is going to be amazing