A) Isis/Seto, the scene in the manga where her willingness to die if she can't save her brother getting him to change his mind about helping Yuugi is what did it.
B) Nah, don't ship her with anyone else otherwise.
C) I don't know, Isis/Yami Malik? Don't know that anyone really does ship that.
D) Don't know what the stupid fandom opinions about her are, so I can't say what opinions of mine would be unpopular with her.
E) Just about anyone really, she's just not interested in that aspect of life.