I think that we should add that only if it is mentioned in the game that she is Thrall's mate.
It's mentioned in the Blizzcon Quests and Lore Panel by Metzen himself they are mated and are going to have kids so.....yeh, pretty canon I think?
3:54 pm Question on Thrall. "Are Thrall and Jaina ever going to get together?" More cheering and clapping.
Metzen: "Think Jaina has some green fever going on?" He doesn't want to spoil anything but he really thinks Golden's "The Shattering" really covers this -- he decides to spoil it, Thrall's going to meet "a nice orc in Nagrand" and have some kids. Question, disappointed says, "He's not Jaina!"
Then Metzen: "What happens to the men that Jaina dates?" Big laugh from the crowd. "THRALL HAS TO LIVE!" So let's put that matter to bed -- "Oh, that's a funny choice of words."