First episode: The Sign of Three
Seen also in: His Last Vow
Occupation: P. A. to Charles Augustus Magnussen
Notable: She's Irish! I love her accent.
Show History: She is first introduced as Mary's maid of honor; when flirting with Sherlock shows no prospects, she enlists his help in finding a suitable man among the wedding guests. During this process, she and Sherlock strike up an unexpected (but delightful) camaraderie. They even flirt a little towards the end, in one of my favorite exchanges in "The Sign of Three":
Janine: "Do you always carry handcuffs?"
Sherlock: "Down, girl!"
Though Sherlock manages to find a man for her at the wedding, to my utter shock (and John's, and the fandom at large), he and Janine are in a relationship in "His Last Vow." Of course (and to my relief, honestly), the whole relationship is a ruse, as Sherlock only wanted to use Janine's occupation as Charles Augustus Magnussen's P. A. to get close to Magnussen. After discovering Sherlock's betrayal, Janine sells exaggerated stories about their relationship to the tabloids and leaves him, settling into her newly-bought cottage in Sussex Downs.
My take on her: I really liked Janine in "The Sign of Three." She was fun, flirty, and even got Sherlock to open up about himself ("I love to dance, I always have done"). She and Sherlock had a really interesting dynamic; it's amazing to see how much their relationship progressed just over the course of a single episode. Sherlock went from being wary and nervous around her (her joke about sex between the maid of honor and the best man really didn't go over so well...) to being comfortable enough to open up and even flirt a little. Watching their friendship progress was a big highlight of the episode for me; I believe in Tumblr-ese it would be referred to as an "epic BrOTP."
And then there was "His Last Vow."
What bothers me most about this episode is how Janine's reaction to Sherlock's betrayal was executed - or, should I say, not executed. Yes, she got her revenge by selling out Sherlock to the tabloids, but we never really got to see her truly, properly angry at Sherlock. He strung her along for weeks, he broke her heart - what person could be completely appeased simply by printing a racy story in the newspaper? What was lacking was a personal reaction - a real, furious, justified response to a broken heart. Instead, she comes across as the cliched, "hell hath no fury," vengeful woman by using the newspapers for revenge, and then forgives Sherlock for the complete asshole he's been to her. I felt like a character I had come to like had been hollowed-out; her reaction was not a true, human, emotional response. I don't know why she suddenly lost the backbone she seemed to have in "The Sign of Three," but she deserved to be angry at Sherlock, to ream him out for being such a jerk to her; instead, Janine wasn't allowed that rage, and I think the character became the weaker for it.
Janine's lack of reaction to Sherlock's betrayal highlights a larger issue within the show - namely, Sherlock's friends thinking so much of him that they never kick him back in line or berate him for being an arrogant jerk. John used to do that, but aside from one line in "The Sign of Three" - "Sherlock, we've talked about this. The showing off?" - I can't think of a single time in Season 3 where John rebukes Sherlock for being an asshole. Mary, revealed as having similar sociopathic tendencies to Sherlock, agrees with most everything he says; Lestrade says nothing, still in hopes that Sherlock will be a great man one day and "maybe even a good one." Anderson used to be one of Sherlock's biggest critics; yet ever since Sherlock's "death," Anderson, consumed by guilt, is now one of Sherlock's biggest fans. Donovan is the only one who still hates Sherlock, and yet she is frequently demonized within the show. The emergence of this problem is another reason why I was hugely impressed when Molly slapped Sherlock in "His Last Vow"; she was taking no more of his crap, unlike so many of the other characters in the show. There's no doubt that she still has a soft spot for him, but she is the closest thing he has to a conscience at the moment, and not just another friend who can't bring themselves to criticize.
But I digress.
As for Janine's future in the show, Steven Moffat seems eager to bring her back, so I'd say it's a safe bet she'll still be around in Season 4. In "His Last Vow" it was mentioned that Magnussen was able to blackmail Janine; I wonder if we'll find out what kind of blackmail he had on her? There's also been speculation that she may be linked to Moriarty, the only other Irish character on the show besides her. Whatever happens, I can only hope that Season 4 redresses the atrocious character writing they left her with in "His Last Vow" and allows her room to grow once again into a fully-developed character.