There is no answer to this, it depends on what you want and how she would react to him or you think she would... i write from experience,..
It is a dangerous game you seek to play,,, trust me.
In my late 20s my best friend a married womaniser made no secret of his desires towards my wife who would be about 23, two young children and the body she had when 17, perfect, no indications of ...... birth. Unfortunately she was often tired so our sex life was poor. Stupidly i mentioned him drunkenly whilst making love to her, her body reacted, her mind didnt. Oh how she had changed from her late teens once the words, married and pregnant were mentioned.
He continued making dirtier suggestions asking me would i like this, NO, i knew she wouldnt anyway was the answer, yet it didnt stop me ...... mentioning him again months later. Her reaction was brutal, she stopped me fucking her and didnt talk to me again for several days. He also told me she had told him firmly to stop talking about this to me, something i suspect most wannabes on here would experience.
So that finished that, except he didnt stop with his dirty suggestions moving overtime to would i like to watch him seduce her, i was now curious and actually now warmed to the idea, so feeling sex starved one day agreed and set a date then regreted it.
Its a long story but on that night ...... over many hours she offered absolutely no resistance to him and he finally fucked my young wife mainly infront of me her dominant masculine 6ft 3 husband. She orgasmed like i had never seen before she liked this that was obvious. The following day there were no harsh words simply...
thats what you wanted to see isnt it?
I allowed him to keep seeing her normally in my absence, i liked this, our sex life improved too. She never acknowledged in detail what had gone on, but he told me all. Then a couple of years later she lied to me when she had no needs i went mental, again a long story.
When it all came out i was shocked,
The first watch for me wasnt their first time.... she had been his FWBs for several years, she being the instigator of when and where,
Shortly after my suggestion to her, she had dropped her bath towel infront of him and asked if he wanted her, so she invited him to fuck her,
His dirty comments were planned to gauge if i was ready to accept her having a lover and it was SHE that decided now was the time, sure i would accept and like this, based on what "my best friend" told her as they lay in our marital bed she full of his cum and tired.
However been a cuck husband for many years i do think she is rare as a "normal" married women and that most wannabes will remain that, its a dangerous game to play and for most there is a lot of wreckage, emotionally, financially and relationship wise along the way.
I knew that i had already ceased being her lover of choice, when she admitted he was her second FWBs, over the years she locked me away in chastity and commenced covertly semi feminising me, something we both still enjoy, yet this helped to finish completely our love making together.
I suspect few achieve a happy long term cuck married like we have.