Confusing people

Someone at work keeps thanking me at inappropriate times. For example, I'll say, "Oh, the painters came in over the weekend." And she'll say, "Thanks."
What? I didn't come in and paint. They did. I didn't do anything!
Or I'll say, as a part of normal conversation and not meaning to be informant, "The CO2 tank started beeping last week! I didn't know what to do!" *laugh laugh*
And she'll say, "Thanks."
??? I can see how you might think that the "thanks" = for telling her this stuff, but it was completely meant to be conversation and that's it. It's unnerving. I don't know what to say.

Few days later...

She's getting nicer and is practicing more socially acceptable forms of communication, so it's better. Phew.