how to comfort an co-employee?

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I have a co-employee who's husband had a heart attack and such event had made him comatose up to this moment. My co-employee is already back to work after she was able to realize that life must go on. Sometimes she talks with somebody in the phone and cry...i do not know what to do further because i think if i comfort her it will just aggrevate her sadness. what should i do?