She'll read that letter, then toss it in the trash right before new dude she's fucking comes over. If anything, he should write the letter, save it, then pull it out years later on some "I can't believe I was all hung-up over *that* woman." Don't let your homeboy mail it to her tho. He minus well show up sobbing on her steps with flowers if he'll gonna go full chump.

Tell your homey to walk that shit off, lol.