She just typed out the equivalent to a doctoral thesis and after reading it, the best reply you could muster up was, "K"? You couldn't attempt to reciprocate her effort with a more thought out text? For some women, that one word text will suffice, but for most, a complete subject plus predicate sentence is the appropriate response. You don't even have to type the sentence out. Just use the talk-to-text function on your phone. She gets a multi-word response and you don't get another dissertation on why your short response annoyed her. It's a win-win scenario.