I can not say that I support cheating in any way.
No matter if you want to put a fancy label on it like "experimenting"
it is still cheating.
And to bow to it, accept it and take notes, means you are ok with an open relationship (?) .
If that is so, then put that rule on the table and enjoy your open relationship. No reason why she should get all the fun and you dont.
Experimenting , is not something you do in a closed relationship.
Take out the fact that, a large number of people find the thought of two women sexy enough that they dont see it as anything 'wrong'
and lets change the scenario to a man , wanting to cheat on his wife with another man.
He calls this experimenting also
I dont think that situation would receive calm, happy responses.
in fact , people would more then likely pull the " you are gay" card and slant the conversation to him leaving her. ( just an assumption! )
lets just say it is a man wanting to cheat on his wife.
People would then talk about how it is destroying the marriage, breaking the home, and betraying a wife's trust.
So why does that not apply here?
She is betraying you if she does it.
If she is just "writing emails" in hopes that you see them........
thats kinda odd
but, if you dont speak up, you will never know the difference.
but I absolutely understand your point of " she may cover her tracks more"
And if she is that determined, she will.
If she is that determined to cheat, there is a problem. And it may not stop at one 'experiment'
How opposed would you be to having someone else in your bedroom?
Are you comfortable enough that you would want to / or feel better if it happened in your home? With you maybe?
Or does it feel right to you to just let it go?