It is almost a certainty that your sister's devotion to the welfare of her children will dilute her anxieties, and the experience of having to confront circumstances beyond their control and overcoming them is a valuable life lesson and achievement she and her children will have in their tool boxes for the rest of their lives.
I hope you reconsider your thoughts about not watching the news. For sure, the coronavirus news is depressing and alarming, but it may help if you regard it as need-to-know information. All over the world brilliant, dedicated medical researchers and medical practitioners are focused on the suppression and eradication of the coronavirus. You wouldn't want to miss the news that they are succeeding.