Britney Spears found out about her 16-year-old sister's pregnancy the same time everybody else did, a family friend says. "This is going to kill her," the friend says. "In the end, she'll be supportive, but this is a big shock." Another source says there's no rift between them, but that Jamie Lynn's advisors have tried to keep her apart from her 26-year-old sister. "Britney doesn't have to listen to anyone now but her sister still does so who knows what people are telling her," says the source. "She has her career now too. Things have been put on hold for Lynne Spears's book about raising her famous daughters Britney and Jamie Lynn, the publisher confirms. "The book is delayed indefinitely. It's delayed, not cancelled," says a spokeswoman for Thomas Nelson, which publishes inspirational books and Bibles. It had been scheduled for a spring 2008 release and was put on hold last week, says the rep. On Tuesday, news hit that 16-year-old Jamie Lynn is pregnant with her boyfriend's child. Publishers' Weekly described the book as "Lynne Spears's personal story of raising high-profile children while coming from a low-profile Louisiana community." The publisher declined to comment on whether the focus of the book would change in light of the pregnancy announcement. "We are standing behind Lynn at this time and understand that she needs time with her family – we support that," says the spokeswoman.