The 78-year-old actress has beaten breast cancer, an addiction to prescription pills and survived a near-fatal car accident, but the one-time Oscar nominee admits she's sure death is just around the corner - and she's fine with it.
Almost unrecognisable as hardcore military ma'am Capt. Doreen Lewis from the Private Benjamin film and TV series spin-off, Brennan is now a frail, housebound pensioner.
She tells America's Globe, ""I've had a wonderful, simply wonderful life and career, and I'm also at a point where leaving this place behind is just fine and dandy with me.""
And Brennan admits life has become quite a lonely existence: ""I'd like to go to the store and see the fruit and vegetables and how colourful they all are, but I don't go. I have no way of getting there.
""I sit on the porch, and I read the newspapers and watch the squirrels play.""
But she feels as if she has been living on borrowed time since she was run over by a car while leaving a dinner with her Private Benjamin co-star Goldie Hawn in 1982.
The horrendous accident left her with serious leg injuries, multiple facial fractures, a broken nose and it dislodged an eyeball from its socket.
Now, 30 years later, she tells the Globe, ""To be honest, I have no idea how I survived. I should be dead, really. Sometimes I wish I was.""
Brennan claims the accident robbed her of her life and she became hooked on strong painkillers that finally led her to rehab at the Betty Ford Clinic in California.
She admits she has contemplated suicide but hangs on for the sake of her two sons.
However, she welcomes death, telling the publication, ""I'm ready any time... Just let it be quick and painless.""