...These three dots, in her view, represent a kind of hesitant, incomplete concern: "What do you want to say? Do you want to control me? Just say it directly. What does sending three dots mean? Let me guess?" Her choice not to reply is her way of responding to you: you remain silent, I also remain silent. Maybe she hopes you'll say directly, "Why are you coughing so badly? Haven't you gone to see a doctor?" or "I heard you coughing, I'm worried." You send three dots, she puts down her phone and waits. Waits for half an hour, an hour, and you haven't said anything else. So she confirms: you have nothing more to say. Then forget it. What she needs is reassurance: either you firmly take care of her (even if you're stern), or you completely ignore her. This kind of ambiguity... makes her feel like you're draining her.

Her mental state summary:
Disappointment: From the previous necessity to check up to... I felt your retreat and hesitation.
Injustice: You cough so badly, yet you haven't shown a single complete concern.
Stubbornness: If you don't say it directly, I won't reply. I don't rely on your concern for me.
Exhaustion: This guessing game has worn me out; I don't want to play this game anymore.