If they are one word such as “yeah,” “sure,” or something along those lines, chances are they’re no longer interested in the conversation or don’t want to talk to you.
It could be that she doesn't want to talk to you, but once again you can't really know what is going on. Instead, they only acquire meaning through the. It might be that she is busy or forgot to answer your message. You can never be completely sure what is going on, though. If there is a long lapse between your text and the response, or if the person doesn’t respond at all, she likely doesn’t want to talk to you.
But by reading responses and seeing how long it takes for the person to respond, you can gauge if the person doesn’t want to talk to you. If you’re texting or using social media sites, you cannot see their body language or hear their tone unless you are having a video call.