Women are either into it or not. I’m in an open relationship and it was mostly her idea.
This story is mostly crud.
Just remember, if she convinces her friend into a threesome for you, that her friend can call that chit in for her boyfriend.
If you do open it up, remember that you each have veto (but only use it if the need is dire, like if it’s your a$$hole friend who you think has an STD he won’t admit to); always talk about it first (“it just happened” is BS. They just thought it was too good to be true)
Lastly, and I can’t stress this enough, never fool around when you are fighting.
Women are particularly bad with this, since they tend to pick partners they connect with emotionally and will want to turn to them if things are rough at home.
Just don’t do that, it can cause perm.