Britney Spears hates being interviewed. Thinks Christina Aguilera is out of line. Says she doesn’t trust anyone when it comes to her music. “I’m really not about fake bullshit anymore,” she tells a startled Blender.

“I can’t believe Christina said that about me,” Britney Spears mutters.

In the December issue of Blender, Christina Aguilera took time out to talk about Spears. It began with Aguilera complaining about how Spears had received all the attention from The Kiss — both former Mickey Mouse Clubbers had locked lips with Madonna during the MTV Video Music Awards, yet the column inches were all about Spears. Aguilera was especially put out that MTV’s cameras cut from her smooch to Justin Timberlake’s annoyed reaction.

“I didn’t even notice that,” Spears says when Aguilera’s comments are read back to her. She puts on her Shirley Temple face and says coyly, “I’m sorry.”

But then Blender reads Aguilera’s next comment: When she encountered Spears recently, she said, she seemed “like a lost little girl who needs guidance.”

Spears is shocked by the quotation; her eyes widen. “That’s funny,” she fumes, “because I haven’t seen her in two years, and then she comes up to me in a club in front of all these people and tries to put her tongue down my throat! I’m like, ‘How are you?’…”

Spears, clearly furious at Aguilera’s put-down, continues: “I say, ‘It’s good to see you,’ and she goes, ‘Well, you’re not being real with me.’ I was like, ‘Well, Christina. What’s your definition of being real? Going up to girls and kissing them after you haven’t seen them for two years?’ A lost girl? I think it’s probably the other way around.”

You can see that half of Spears knows she shouldn’t be saying this, but Aguilera’s offhand comments have clearly hurt. She stops and apologizes, then, unable to resist, kicks off one last time: “When somebody’s been rude to you so many times, it’s like, ‘You know what, Christina? I’m really not about the fake bullshit anymore. You’re scary and I feel really dark when I get around you, so I need to be over here now.’ ”

The outburst is, in a way, a relief.

Because Britney Spears has finally said something she really means.

Up to this point in our interview, Spears has maintained an icy self-control. Lipsticked and expressionless, she walked into the room chewing gum, sat down, put her boots up on the table and gazed into the distance. Brusque, you could call it. The sort of entrance that makes you think, This is going to be tough.

So it was. Up until the Christina outburst, Spears had answered questions politely, though sometimes huffily. A few times she didn’t even reply, or said, “Your point is?” Or, bluntly, “That’s a personal question.” Followed by silence.

You ask how many cigarettes she smokes a day. She says curtly, “Nine million.”

Nine million, huh? You must have lungs of steel.

“Yep.” Then, “I don’t fuckin’ know. I’m sorry if I seem a little bit bitter,” she says in her least apologetic voice, “but I’ve done a million interviews, and it’s the exact same question every time.” She draws a breath. “Are we done yet?”

We’ve barely been with her 20 minutes at this point.

To see more frightening outbursts from the pissed-off Princess of Pop, pick up the January/February issue of Blender, on newsstands now!