TMZ broke the story ... the intervention that was planned would include her husband, Sam Asghari, her manager and medical professionals. Her manager rented a house in the L.A. area where the intervention would go down, and the plan was for Britney to live there for around 2 months to get better, but someone in her camp pulled the plug on the plan.

As we reported, Britney's behavior has become increasingly erratic and volatile ... the result of her mental illness and substance abuse.

Here's what people with direct knowledge tell TMZ ...

-- "The intervention was long overdue. She is very much a danger to herself and those around her. It's a ticking time bomb. Thank god somebody finally took some steps to do something about it."

-- Another source says, "I worry about waking up in the morning and feeling like I'm going to get a horrible phone call."

-- A third source says, "This is 2008 all over again. There is serious fear she is either going to die or kill someone. She is abusing caffeine, Adderall, and anything she can get her hands on. She is not taking her medication, which is essential to stabilize her mood and is unknowingly trying to self-medicate with other substances, which is exacerbating her mental illness."

-- And finally, "She has unbelievable untreated trauma that with the help of therapists and specialists could put her in a much better place. An intervention is essential to make that happen."

There is anger among those who believe an intervention is necessary ... anger that someone has derailed the plan, and they are not giving up.