This storyline really bothers me because in no world should there be any type of chemistry between Barney Rubble and a knockout (a 10). So, I dissected it and came to the realization that it was manufactured by Ade intentionally. She realized she's in love with the nephew/cousin of a mob boss, and contrary to popular belief, she was not as naive as people like to make her out to be. She was definitely a saint in her actions, but she definitely wasn't a complete and total stunad. She always knew of the life the men around her lived, what they did, why they did it, and maybe even a little bit of how they did it. She wasn't some random girl from Jersey. She was the niece of the famous Jackie and Richie Aprile, and growing up fatherless, they must've been father figures to her and present in her life, representing the two different sides of the men in the mob and, more importantly, the two different sides of a father, until Richie went to jail. So she was deprived of that psychopathic, narcissistic, sick fuck vibe, influence, ... love.
Hence, her eventual relationship with Christopher, who mirrored Richie to a degree that made it almost uncanny. They were both extremely short-tempered, violent, narcissistic, and hypocritical (Richie getting mad at Chrissy for beating Ade before they're married when he full-on punched Janice in the mouth shortly after this, and there was no ring on her finger either). She never left Christopher for treating her like shit because it reminded her of her uncle Richie who was like a father to her. She wasn't a masochist or anything, but subconsciously, she felt a sense of familiarity and connection to Christopher when he beat her, even if she physically recoil in pain. As for Christopher, he treated her the way he did because he was a narcissistic sociopath.
Now that we have Adriana's psyche mapped out, and the motivations that come with it, let's discuss the big purple dinosaur in the room. Tony represented something she thought she already had in the form of two different people in her life: first Jackie Sr., and now Tony (two older, protective, alpha male figures). Except, as we all know, and I'd argue Adriana realized at some point between becoming a rat in S04E02 and S05E05, that Tony was no Jackie Sr. He only pretended to be. Sure, he was older, but with his protection and alpha male behavior came his little cannoli too, and he wanted to fuck her fucking brains out with it.
The fact that he was divorced, emotionally unstable, and looking to restart a family with a younger, hotter broad (as the ultimate fuck you to Carmela) only added to his attraction to Adriana, and I think on some level, Adriana understood all of this and used it masterfully.
After she flipped, in the timespan between S04E02 and S05E05, she knew she'd be killed for it and there was no way out. Without a shadow of a doubt, she did. And she didn't tell Christopher immediately because she knew what Uncle Richie would've done to her if he knew she flipped, and she didn't tell Tony either because by then she knew he was no Jackie Sr. She was between a rock and a hard place, the hard place being Tony's cannoli.
People often debate what would've happened if they hadn't crashed in S05E05. And I think I finally figured it out. She wanted to get him absolutely wasted on coke. That's why she immediately obliged when he offered to drive her there. She already had a ride on the way. Why get an already coked-up Tony Soprano to drive you there unless you wanted to do more coke with him.
I think, she wanted to get him absolutely wasted on coke so he'd let his guard down completely. Then she'd use whatever means she felt were necessary (sexual acts) to get this already emotionally unstable and coked-up Tony Soprano to form a sort of bond with her build through his favourite thing in the world (sex), that she coud later exploit to get him to discuss business with her, which she could later share with the feds and get him put away. But they crashed, and all that other bullshit happened, and Tony got put in horny jail around her, at least visibly, for the rest of her life (which wasn't too long after the crash).
So the way out through seducing him also closed on her, and she was genuinely left with no option but to approach Richie (Chrissy) when shit hit the fan with Matush and the feds inevitably pushed her harder than ever to flip completely. And as she always feared and knew, Richie pulled a Richie and had her whacked (because Chris had his own case of the frog and scorpion).
Ultimately, I think Adriana was far more complex than she let on and genuinely street-smart, but lacked a lot of what people understood to be knowledge that came with having common sense. Hence, people always looked down at her as if she were a stunad of the largest magnitude (not knowing Matush was a terrorist, not knowing Christopher was fully unfaithful with her, etc., etc.). But every instance that's supposed to prove she was "naive" just proves that she lacks knowledge, either because her heightened compassion blinds her to it or because her lack of homework in that particular field has led to her not understanding how it works.
I'm not debating the effectiveness of her proposed plan in this theory of mine (in my personal opinion, it would've failed spectacularly and probably gotten her killed by Christopher for sleeping with Tony, which is sad because she literally would've done it for them). All I'm trying to say is that she was nowhere near as naive as people make her out to be.
Naivety and lacking knowledge in many different fields are inherently different states to be in, but because they have similar repercussions, people often act as if they were interchangeable states of mind.
TL;DR: Ade was never truly attracted to Barney Rubble. She just thought she could use him to get the life that she wanted for herself and Christopher. This is partly why she became upset so quick with her handler in the next episode when her handler suggested exploiting the newfound relationship with Tony to get information. And the reason for her reaction to the statement being negative was because there was never a relationship (just a failed attempt at a one night stand with a very important reason at its centre), and when it wasn't recognized as such this disgusted her. She saw Barney Rubble as a means to an end, but when that means closed on her, not that it would have brought her to the end that she sought, she inevitably met her demise.