It's not just her boyfriend that you'd be making happy, is it?
She's dating another man at your request - your cuckold fantasy is powerful, after all - but you know that she's found something with him. You know that he satisfies her in ways she didn't imagine possible.
Of course, you love having sex with her. It feels so good to slide into her after he's been inside her. It feels so good to know that your cock is bathed in another man's thick, creamy load. Could you really give that up?
It'll be hard, but of course you can give it up. You can be the cuckold she needs you to be. You can be pussy free for however long she's with him. You can be the kind of man she needs you to be.
I wonder, though, if he'll want more. Perhaps he'll ask her to spend more time with him. Perhaps he'll ask to sleep in your bedroom more often, kicking you to the couch when he does. Perhaps he'll try and become the only man in your wife's life.
There's always a risk with cuckolding. Are you willing to take that risk to live out your fantasy?