There is no reason to think Meetra's opinion is based on imagination.
- She herself had a similar connection to the Force as a wound.
- She faced Nihilus.
- She learned from the people who knows Nihilus more than anyone else: Kreia and Visas.
- She knew Revan well enough to easily have a very clear opinion on him.
- She doesn't have a motive to lie or be delusional on this matter.
In other words, your skepticism on Meetra's opinion is unnecessary.