The woman suffered minor scratches and one of her dogs was wounded after tussling with the 200-pound bear.
The attack happened just after midnight when the woman let her three dogs into the backyard for their nighttime ritual before she headed to bed, Missoula County Sheriff's Lt. Rich Maricelli said. Authorities believe the black bear was just 25 yards away, eating apples from a tree.
Two of the dogs sensed the bear, began barking and ran away, Maricelli said. The third dog, a 12-year-old collie that wasn't very mobile, remained close to the woman as she stood in the doorway of the home near Frenchtown in western Montana.
Before she knew what was happening, the bear was on top of the dog and batting the collie back and forth, Maricelli said.
"She kicked the bear with her left leg as hard as she could, and she said she felt like she caught it pretty solidly under the chin," Maricelli said.
But as she kicked, the bruin swiped at her leg with its paw and ripped her jeans.
The bear then turned its full attention to the woman in the doorway. She retreated into the house and tried to close the door, but the bear stuck its head and part of a shoulder through the doorway.
The woman held onto the door with her right hand. With her left, she reached behind and grabbed a 14-inch zucchini that she had picked from her garden earlier and was sitting on the kitchen counter, Maricelli said.
She threw the vegetable. It bopped the bruin on the top of its head and the animal fled, Maricelli said.
The woman called for help from a relative staying with her. They found the collie outside, unable to move, and took it to a veterinarian.
The dog appeared to be fine on Thursday, but the vet was keeping it for observation, Maricelli said.
The woman did not need medical attention for the scratches on her leg, though she got a tetanus shot as a precaution, Maricelli said.
Montana Fish, Wildlife and Parks officials set up a trap in an attempt to capture the bear, the agency said in a statement.
Besides the nearby fruit trees, there wasn't anything on the woman's property that would attract a bear into the backyard, like garbage or livestock feed, wildlife officials said.
Maricelli interviewed the woman, but said the sheriff's office was complying with her wish not to identify her.
"She was very, very shaken, and it kind of took the humor portion out of it for me," Maricelli said. "She said it had this horrific growl and was snarling.
"(But) she can see the humor in it, and she wanted the story put out so the local residents can take precautionary measures," he added.