Hello there! It sounds like Karen is suffering from GAD, or Generalized Anxiety Disorder.
GAD is defined as "Severe, ongoing anxiety that interferes with daily activities." That can refer back to the text saying her worry "tends to interfere with her daily functioning." Along with that, the symptoms she's experiencing, stomach aches and insomnia, are also symptoms of high levels of anxiety, so it sounds like this is what she'd be diagnosed with by a medical professional, if she went to one.
I hope this helps and have a great rest of your day!