Question

According to one Teen, "you can think about a text and you cannot respond to a text if you don't want to talk to someone" what she means by this is that :

Answer 1

You can (have the permission, or a possibility) to think about a text.
If you respond a text, someone will answer you. (it´s a logical conclusion)
So, 
if you respond, it means you want to talk to someone.