Super annoyed with my coworker

Went into work not feeling good at all, she offered to stay late so I could go home early and I thought about it for awhile because I felt bad, but then decided to leave early and when I told her that she went on and on how she was supposed to go to the store today because her husband is at work and her son is at school and today was a good day to go... like why offer to stay for me if you're just gonna throw in my face what you were supposed to do today? Ugh