While I agree with your mom that he is so wrapped up in the affair he simply doesn't know or care what effect it has on anyone, I dislike her choice of the word love. While I can't deny the statistics that show affairs often end in marriage (mine nearly did!), I really feel that MOST affairs are infatuation and obsession masquerading as real love. It is emotionally abusive, but I'd like to qualify that it may not be deliberate. I know that's not much comfort, but it may make a difference how you feel about it in the long run.
The grass may be greener, but then again, it may also be astroturf. ~Amy C Brown