Seeing these two together is what got me into "Straight Shota" pairings...even though I'm sure that is not the reason why they were alone together in the middle of the story, and that they had to go through enemy territory (while Hope was still busy thinking about vengeance against Snow)...
To think that romances involving a young boy and an older woman are all considered "child abuse" by most people...I think it really depends on the people in the relationship itself.
Cloud and Lightning have the different personality.
Like Luka said wisely, they are like brother and sister to each other. She may acted like a mother toward him 'cause she taught him how to fight and be there for him. It's hard to tell which sister or mother would she be to him.
Everyone have the different opinion. I would suggest the both sister and mother. lol.