Why is she always playing the victim of your carelessness?

My co-worker sets it up that way with her half-truths and doesn't say what she means...won't use her words. Example: she says "can you help me move a table" you're like "sure no problem". So you go help her move the table and move on to another task thinking job well done. But she really needed help with three tables (she only said one table) then when the boss shows up everyone feels sorry for her and acts like you wouldn't help her and you're the bad guy?