Texts then doesn't answer

Can anyone - preferably female - help me figure out my coworkers feelings?

Over the past six months or so I've developed a friendship with my female coworker (she is 26, I am 32). A few weeks back we went for a walk, then yesterday we spent ten hours sat chatting and enjoying a drink together. After I dropped her back home, she texted to say she had a lovely day and enjoyed it. I responded to say I too had enjoyed it, but she has not been online for nearly 24 hours now and not bothered to read my response.

As a woman, what does this mean? Why would you say you'd had a good day then ignore the answer? As context, yesterday was the first time she'd confided in me that her last relationship ended a year or so ago after she was cheated on twice.

Edit - she finally checked my message before arriving at work but didn't bother to respond and appears to be indifferent toward me at work now. I'm not sure what I've done wrong.