Britney Spears' Cousin and Former Assistant Alli Sims Speaks out Against Dad Jamie Spears

Britney Spears' cousin and former assistant is speaking out in her first interview in over a decade, claiming that the pop star's father, Jamie Spears, forced her to cut off all contact with Britney. Alli Sims opened up to NBC News Saturday in the wake of The New York Times documentary chronicling Britney's conservatorship battle, Framing Britney Spears, claiming that Jamie "100 percent was threatening me with my life" when he insisted she cut off communication with the "...Baby One More Time" artist.

Britney was going through a difficult time when Sims says she was forced to cut ties, going through a custody battle with ex-husband Kevin Federline, experiencing mental health issues and being placed in two involuntary psychiatric holds. Sims said of her agreement to step back, "I really do believe [Jamie] would have done something if I didn't remove myself from the situation."

Britney is currently embroiled in a legal battle to remove her father as the sole conservator over her estate, asking the court to appoint a third party financial institution in that role. The artist's attorney, Samuel D. Ingham III, has claimed Britney is afraid of her father and will not perform until he is removed as the sole conservator. Sims told NBC that she misses her cousin deeply, and knows that if she ever comes forward to tell her story, people will be shocked at the whole of it.

"When I think about how long she has had to endure this and it being 13 years, it just makes me so sad for her. I really do hope one day she's able to tell her story if that's what she wants to do," explained Sims. "If she does, get ready because there's more to that story than I'm sure anybody could ever imagine."

Following the release of Framing Britney Spears, the star's longtime boyfriend, Sam Asghari, spoke out against Britney's father in a rare statement from their side about the ongoing conservatorship battle. "Now it's important for people to understand that I have zero respect for someone trying to control our relationship and constantly throwing obstacles our way," Asghari wrote on his Instagram Story last week. "In my opinion, Jamie is a total d—. I won't be going into details because I've always respected our privacy but at the same time, I didn't come to this country to not be able to express my opinion and freedom."

Jamie has denied all claims of financial abuse to CNN, telling the outlet in December, "When a family member needs special care and protection, families need to step up, as I have done for the last 12-plus years, to safeguard, protect and continue to love Britney unconditionally. I have and will continue to provide unwavering love and fierce protection against those with self-serving interests and those who seek to harm her or my family."