My sister has already worked. How can I comfort her with words?

In fact, sincere concern is far from being expressed in words, so you may get a satisfactory answer when you ask online, but it is not what you want to say to your sister. There is no need for sweet talk between relatives. If you know that your family is hard, tell her yourself, "Sister, you are hard, don't be too tired, pay attention to rest more" and so on. A simple sentence does not need to be taught by others, from the heart, say thank you to your hard-working sister!