Although I know many disagree with me, the whole Theramore/Tides of War story has had me worried from the get-go, because I for one have always really liked Jaina for her peaceful & sympathetic nature.
Blizzard has strongly advanced the theory that we would see her abandon her beliefs & become more of a warmonger-type who is focused on getting revenge on Garrosh (and that putting her in charge of the Kirin Tor was possibly a big mistake). I haven't read Tides of War, and I haven't heard much about the Kirin Tor saga in Patch 5.1, so I don't know if this has indeed happened. I'm going to find it hard to support Blizzard's story team if this is how they are going to "develop" characters like her.
However, I have heard some reports that it's implied that Jaina really hasn't changed a lot, she's just even more emotionally scarred & holds a justified grudge against Garrosh (much like how Thrall hates Varian, but is very different from Garrosh). (Christie said she has a "very strong core" which makes her different from Garrosh, whatever that means).
Christie also said in the interview that she felt that Jaina has found her true place in Azeroth. My Mom hasn't read Tides of War yet either, but she has gotten a strong impression from Christie's past novels & interviews that she really sympathizes with those lore figures who resent Varian & Garrosh's lack of compassion/Blood Knight attitudes...so she really doesn't think that Christie would say that if Jaina had abandoned her beliefs or was going to be portrayed in an antagonistic light in Mists.
As far as I'm concerned, it's either an overhyped event, meaning that Tides of War details Jaina's response to grief (but ultimately she emerges with her compassion intact, even if she is traumatized & anti-Garrosh), or it's just flat out one of the worst decisions I've ever seen any franchise make about a single character's development. The second worst being the decision to make Garrosh Warchief in Cataclysm & in turn make all of the new Horde quests have much more of a "bully" feel to them.