This is purely hypothetical for me, but I thought it posed a good question before it got zapped. So considerate it a re-post of sorts. Details fuzzy (and possibly not entirely accurate) because they weren't fully fleshed out.
Suppose BM is absent. She's off indulging in some sort of party lifestyle, in and out of drugs, doing her thing and rarely seeing or talking to her child. BD and CSM have custody of the child, who is a teenager. SK toes the line in BD's presence but gives CSM trouble behind dad's back. BD is intending to work out of a town for a few months duration and will be mostly out-of-pocket since the job requires his effort seven days per week. He may make it home for a weekend or two, but CSM can't count on it. Since he doesn't observe SK's disrespect for CSM, he doesn't "get" the problem. What should CSM do? Is she being selfish (bad wife, evil SM, etc.) to not want him to go?