it's none of my business in either case... so i wouldn't say anything..
funny thing is that scenario b happened to me with a family friend.. she was secretly dating someone while we were in college i saw them together, but figured its not my place to say anything.. she kinda fell off the wagon.. she started drinking smoking etc.. and before she was not like this.. i heard that she pretty mcuh ran away from home, to be with "the man of her dreams." i don't stay in touch with the family as we've moved.