Girls, Why did a female co-worker look sad when she thought I had quit my job?

Someone told me from work she seemed concerned when she thought I quit my job. Her response was like an "oh no" response and saying my name. Her behaviour went all reserved towards these people. But then someone clarified it wasn't me that quit my job. She was relieved. What does this mean?
Girls, Why did a female co-worker look sad when she thought I had quit my job?
Post Opinion