Originally Posted by Pack19
She made a comment that I understand our separation was necessary.

I agreed


Originally Posted by Pack19
I must realize the separation was necessary. I validated those or at least I think I did.


Agreeing separation was necessary does validate her. If that's your position--if you'd go back in time and say, "Paco and Paco's W, I'm you from the year 2020! With hindsight you two SHOULD separate"--agreeing is sensible. Note, you can also validate her without agreeing with her.

Originally Posted by Liam @ StackExchange
When you agree with someone's thoughts or feelings, you essentially take it on as your own. If I were to show you a ball and say, "The ball is blue" and you agreed with me, you would be saying that you also believe the ball to be blue.

Validating someone's thoughts or feelings is something used quite frequently in psychology and counseling, and is regarded by some to be a bit of an advanced communications skill that really relies on active listening.

By definition, you validate someone's thoughts or feelings by acknowledging that they make sense and you understand where they are coming from. You don't have to agree, nor do you have to take them on as your own. Additionally, it doesn't require you to actually defend someone's thoughts or feelings, but it does help during the communication for you to go over some of the reasons as to why they might think or feel the way they do.