Despite maintaining a close relationship with her ex-husband, radio presenter Chris Evans , the singer-turned-actress would not allow her new husband Laurence Fox to do the same.
She said: "I'd be furious! I'm a jealous partner. You're entering serious bunny boiler territory when Laurence even has to hold hands with a girl he's working with.
"Laurence is just far more relaxed, so much cooler than I am about that kind of thing - it's a testament to who he is really."
Discussing the infamous incident when Chris arrived at the hospital just after her first child Winston was born, Billie told The Observer: "Most relationships would struggle with that.
"I think that what happened is very simple acts of friendship get framed in a certain way.
"Chris has been such a big part of my life that he's always there when the big things happen, but that might make everything look more full-on than our relationship actually is. I barely see Chris now."