Dec. 19, 2007

Is your neck sore from all the head-shaking you've been doing since hearing the news that Jamie Lynn Spears, the 16-year-old sister of court-monitored cautionary tale Britney, is going to be a mommy?

Yeah, ours is, too.

But apparently we weren't the only ones stunned by the high school junior's jaw-dropping interview with OK! magazine, in which she revealed she's three months pregnant with the spawn of erstwhile boyfriend Casey Aldridge (TMZ.com believes she's actually further along, predicting a spring arrival).

Seems Brit, 26, was also in the dark about the unplanned bun in Jamie Lynn's oven, finding out about it on Tuesday, the same time as the rest of the world.

TMZ reports the maternal-instinct-lacking mommy of two was "frantic" over the news, while Perez Hilton says she personally called OK! magazine to try to get a copy of the article.

But Britney looked anything but distressed when she stepped out Tuesday night in Los Angeles for some paparazzi-documented retail therapy, hitting the Lisa Kline boutique amid the usual crush of cameras.

"She called us in the early evening and said she wanted to come shop for Christmas," a store staffer tells People. "She looks the best I've seen her in a really long time ... She was really, really nice, saying, 'Thanks, babe,' 'Yeah, babe.' Everything was 'babe.'"

However, when shutterbugs questioned her about Jamie Lynn, Spears, who's currently sporting two-toned extensions best described as Pepe Le Pew-esque, played dumb -- a stretch, we know.

"My sister's not pregnant," baby-talked a goofy-face-making Brit, who maximized her well-timed photo op by donning a different ensemble upon exiting the store. She then added for emphasis, "What ever."

A source clarifies to TMZ that she was just "being sarcastic" with the snappers and was well aware of the pregnancy.

Jamie Lynn Spears and Casey Aldridge at a Los Angeles Disney benefit on June 10

That would explain a statement released to E! News right around the same time (seemingly by one of the few remaining members of her inner circle), in which she said she "wishes her sister nothing but the best and asks for privacy during this time."

It remains unclear whether she's asking for privacy for herself, which isn't likely to dissuade the army of lensmen who track her every gas station stop and hotel check-in, or for her little sis, who pretty much lost the right to privacy once she discussed the contents of her womb with OK!.

Meanwhile, a "family friend" tells People that Britney is reeling over her "Zoey 101"-starring (for now anyway) sibling's bundle of oy.

"This is going to kill her," says the snitch (and not, it seems, because it steals her train wreck thunder -- well, probably not just that). "In the end, she'll be supportive, but this is a big shock."

What's likely going to be a bigger shock is that her custody-retaining ex-husband, Kevin Federline, who remained on good terms with his former mother-in-law after the bust-up, may have been privy to the baby bombshell.

"Kevin knew before Britney that Jamie Lynn is pregnant," a K-Fed family spy maintains to Page Six. "In fact, Britney's mom Lynne told Kevin about it on Monday [Dec. 17] because Lynne wanted Kevin to be prepared when Britney found out."

Says the source, "We're waiting for the fallout from Britney. Kevin is sure Britney will flip out and blame her mom and dad."

Speaking of her dad, he's apparently trying to stay above the OK! fray.

A "source close to the family" informs Us he's "furious" with ex-wife Lynne and Jamie Lynn for blabbing to the magazine, which TMZ reports didn't pay for the sit-down but will fork over a million bucks to the new mom for the exclusive first snaps of her little nipper.

Papa Spears is also said to be "devastated" and "extremely depressed" because he "feels Jamie Lynn ruined her life."

Adds the not-at-all-biased insider, "He put his foot down and refused to take any money and 'profit off of his children.' Lynne didn't care."

As for Britney's relationship with Jamie Lynn, it remains distant, according to People, with a mole claiming the teen's "advisors" (probable translation: mom Lynne) have kept her away from her bad-decision-making big sis, whom she hasn't been spotted with for a couple of months. 

"Britney doesn't have to listen to anyone now but her sister still does so who knows what people are telling her," the source tells the mag. "She has her career now too."

Jamie Lynn, for her part, was spied in New York this week taking in an educational documentary a movie with her mom, whose laughable plans to write a parenting guide have reportedly been put on indefinite hold.

Page Six reports mother and daughter caught a screening of the critically hailed teenage pregnancy flick "Juno."

Next: Romance Report: Justin & Jessica Shacking Up?