This is the reason

During marraige when pandit said the girl he is gonna marry will love him more than her life like something. Vandana was not happy with this. I read many post why vandana was not seeing maya has beyhadh love for him.
I think this is the reason. She predicted it beforehand but the way she behaved with maya is wrong
p.s. I'm not supporting any of vandana's actions during and after marraige.