The title of your post suggests that the concepts of OCD and coping strategies are mutually exclusive. Unfortunately, they are not. Although ultimately maladaptive, the repetitive behaviours associated with intrusive thoughts and fears are often used as a way of coping. Excessive Self-Care's sister-in-law may indeed be using showering to cope with intrusive thoughts and even if this behaviour "soothes" her thoughts, the effect is only temporary, which could account for the repetitive behaviour - showering multiple times a day. My point being, this isn't necessarily an either/or situation, it could be both.