I find it curious that someone can disturb others on a bus with loudmouth conversation, and the victim is being blamed! While I probably would not have done what you did, Goq, I nevertheless totally get why you did it. This woman might have been totally unaware of how loudly she was speaking, but that doesn’t mean it should not be pointed out to her. The problem is that people who are so thoughtless (talk on cell phones in restaurants, have loud conversations in public, play loud music late at night, etc.) never recognize in themselves that they are doing something that bothers another person. And if they do, they clearly do not care!
I would have said something on the bus, more along the lines of, “I don’t know if you realize it, but everyone cannot help but hear your personal business.”