When I started watching I thought for sure it was going to be the dog barking its head off a these bears. But, no, this dog decided to be all bad ass from the get-go and actually head butted the first bear he came to!
As ridiculous as this video looks (and sounds), her response is similar to how I've responded to bears while cycling alone in the woods. I find myself just yelling the obvious at it because it's a reason to create noise. If I suspect a bear is in the area while passing through, I will usually sing something like "go away bear, I'm just passing through, la la la don't wanna see you bear!"
If you have not seen "The Woman Who Wasn't There," the documentary about "Alicia Head," I heartily recommend that you check it out. I believe it's available on Netflix.