I understand what you mean but that's not emotional cheating, no, since Myles made sure to tank his relationship with Abel. The disliking and dissing Abel part seems odd? Man didn't (doesn't? depending on what dialogue you pick?) seem to even fully know Myles' conflicted yearning for him before the game.
Myles' inability to face his forbidden same-sex attraction (internalised homofobia?) towards his ex-BFF ended up hurting both Diane AND Abel for years :<