There's a couple things that can be said in regards to whether it's an A or not:
If you do not know if you are having an A, just ask your spouse.
and...
When there is something to hide about a R, then it is most likely an A.
It is the hiding that really makes it real for the betrayed spouse.
If they talk openly about their R with the OP... then no big deal. Of course, if there is a lot of "consol" going on between a spouse and an OP that excludes the BS, then that's similar...
"Hey, OP is having a melt down. Want to come with me to visit with OP or do you want to invite OP down for supper?"
Anyhow, it's not to convince you that there was something more going on or not. How you feel about the OP is how you feel. In a "perfect" world, you would let your W know that her R with OP was feeling uncomfortable with you, she would empathize with you, and she would either include you or reduce or remove her R with OP...
While she told you she had... something started them chatting again and she did not let you know... as though having "forgotten" that R made you uncomfortable.
So...
No matter what did or had happened... the reasons... the circumstance...
This is where the work begins...
What are you now... aside from burying yourself in work... going to do?
Having read DR... do you feel you need to use LRT right now?
What 180s do you think you might do?
Aside from work, what kind of GAL... and don't use "I can't because I have work" excuse... what do you plan to do in the GAL department?