I think she was right or I think she is right? [duplicate]

I would say that this depends on how much time has passed. Both can be correct given a context.

If the statement was made recently, is/are would be more correct. If a period of time had passed, was/were would be better.

If I would give an arbitrary number, I would say "recent" would be with in the day, or even stretching to within the week, however any longer would be was/were.

Also to complicate it a little more, if recent and said colloquially, often native English speakers would shorted the statement to, "My friend's correct" or "You're correct" rather than outright enunciating the word "is" and "are".

I hope this answers your question.