The husband and I were talking about this last night, and he has a vastly more healthy approach to this than I do. He says that since it doesn't really affect him, it's not his business and won't make it so. Let go and let God (so to speak, we really need an atheist version of this saying).
I admitted it's a real source of resentment for me. I think it's partly because I always felt like I got the short end of the stick in my own family and I'm really protective of myself and my needs when I feel like it's happening again. So I'm trying to slough it off and not get emotionally invested in the drama. I'm a grown-*** woman with my own family and responsibilities -- why should I caught up in this?
It's just so hard when the parents rearrange everything to make sure SIL is involved/comfortable/happy and SIL is consistently late/selfish/making excuses for crappy decisions. Just last night, we celebrated my husband's birthday with a dinner out. She bragged about how drunken and rowdy her weekend was -- directly after the drunk driving accident, remember -- after arriving 45 minutes late, and left early after the free meal was over. Her recent behavior just reads on the alcoholic spectrum for me so clearly, but the rest of the family thinks she's "just" a binge drinker and doesn't have a "real" problem like my husband did (a slow burning addict), and it makes me crazy to sit there with my mouth closed during family functions. She called herself an alcoholic last year, but went back to drinking when she realized she's actually have to make life changes to deal with it. The rest of the family is pretending all that never happened or is chalking it up to her immaturity. We're not at the point yet to cut off all family ties, but I feel like it's irresponsible to pretend like this isn't the elephant in the room.