You're absolutely right, we should invest our emotions in people who will value them. Well, in your sister-in-law's case, I would say you did nobly, you know, had it been you didn't try your best for her, and unfortunately, a bad thing occurred, you would have blamed yourself for the rest of your life for not offering to help, but right now you're guilt-free. What I can advise you is to love without being attached.