Jamie Lynn's Baby Countdown!

As Britney Spears continues her recovery in L.A. — going to the gym,

the recording studio and taking occasional acting jobs (her guest appearances on the CBS sitcom How I Met Your Mother could earn her an Emmy nod) — her little sis, Jamie Lynn Spears and her boyfriend Casey Aldridge have been preparing for the arrival of their baby girl.

They've moved into their new home in Liberty, Miss., the town where Casey grew up and most of his family still lives. It's only 30 minutes from Kentwood, where mom Lynne Spears lives at Serenity, the estate Britney owns and where Jamie Lynn was raised.

The couple's new $300,000 house has four bedrooms, a large yard and a swimming pool, something Jamie Lynn told OK! was an absolute essential.

"I love to swim," she said of her favorite exercise. Britney will get a tour of Jamie Lynn's new home but will stay at Serenity with her mama, Lynne. Although she'd love to visit for an extended time, she'll return to L.A. after just a few days.

"Britney will almost certainly have to juggle some of her visitations with her kids while she's off seeing her sister and new niece," an insider tells OK!. "She's not going to want to miss too many of those."

But don't think the singer isn't chomping at the bit to meet her new little niece!

Sources say Brit is set to hop on a chartered jet as soon as she knows that Jamie Lynn, is in labor and has already packed her bags.

Ever since Britney, 26, made a quick visit to her hometown of Kentwood, La., on May 3 for her 17-year-old sister's baby shower, the girls have been in regular contact, mostly texting, about the pending birth of Jamie Lynn's baby girl.

While there are no plans for Britney to be in the delivery room, she hopes to make it to Louisiana before Jamie Lynn delivers.

"As soon as she knows Jamie Lynn is in labor, Britney and her dad will be on a plane," a source close to the family tells OK!.

For more on Jamie Lynn's baby countdown, pick up the new OK! — on sale everywhere Thursday!