Comfort her, listening is more important than telling. A depressed heart needs our listening ears. Listening is listening to each other with your ears and heart. Remember one thing: never ask her why she is upset, and don't rush to make arbitrary thoughts according to the situation at hand. Give the other person more space so that she can express her feelings freely.
The so-called heart-to-heart communication means empathy with her, and she will notice your inner fluctuations. If our mood fluctuates with her: such as sadness, his sadness and happiness, his happiness. This is the best guide for her to get lost.