Britney Spears had to be convinced, cajoled and even badgered into giving rehab a fair shot. We're told three people may have made all the difference.

Britney's mom, Lynne Spears, has been frustrated but undaunted in trying to convince her daughter that she had a problem and needed help. Before Kevin took custody, it was Lynne who protected the children. She has also made Britney and the kids the priority in her life. Britney has railed against her mother; but Lynne refused to back down.

We're told uber-lawyer Laura Wasser stuck with her client as Britney appeared to self-destruct. Many lawyers are notoriously impatient and even intolerant with clients who defy orders and reason. Wasser must have figured out Britney's problems were bigger than she -- and stuck by her side.

Kevin Federline has also been a staunch supporter of his estranged wife. According to several sources, K-Fed has "stepped up to the plate" in Brit's time of need, taking care of the kids and offering Britney and her family support. He has also shown the pop princess tough love; denying her access to their young boys, even when she begged him for it. That, our sources say, was excruciatingly painful for Kevin, but he knew it was the best thing for his wife and his children. We're also told he is being "extremely reasonable" in the divorce.