Source: Britney Hasn't Slept Since Saturday

Originally posted Thursday January 31, 2008 09:20 AM EST

Britney Spears's latest trip to the hospital appears to be turning out much differently this time: The pop star went willingly, and she's "more comfortable" receiving medical care – even making a joke about her second trip, a source close to the pop star tells PEOPLE.

"She'll be in there for at least 72 hours getting evaluated. She might even stay longer," says the source. "She's more comfortable this time, she came into the waiting area, had a cigarette, made a joke about being there again. But who knows what will happen. All we can hope for is that she gets better."

Even the logistics in getting her help and getting her to the hospital were planned better – and far in advance, according to the source.

"Something like this has been in the works since the [last trip to Cedars-Sinai Medical Center]. She has been seeing her psychiatrist every day," the source says. "No one thought this would happen this soon, but it was clear if she stayed up for more than three days she'd have to get sent, since that could cause real damage. The last time she slept was Saturday."

Adds the source: "The motorcade and everything was planned, it was already in the works to have them block off the road and airspace. It worked out perfectly."