I share an office with someone who handles stress poorly?

She's a nice lady. She means well. But she tends to judge people harshly. I take it personally even though it's not about me. When she gets stressed out, she bosses everyone around, even though she's not the boss. She brags about how she works long hours every day. The thing is, she doesn't work on her job, just everything else, (personal phone calls, stuff she has to do for home, etc.) so she has to stay late to do her actual job. She's a brown noser. She likes to point out how she does all this extra work for free and expects everyone else to as well. In response, I said, "This job can replace me at any time without feeling an ounce of grief. My kids never could. I'm going home to see my kids." Sometimes I think she's great. but sometimes she's a bear. I think thats the hardest part. I never know what to expect. How can I diplomatically address this with her?