Lonely rats. What to do?

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My little rat is being sprayed in a couple weeks and she will have to be separated from her cage mate for about a week after the surgery. They are best friends and love each other very much. I am worried they will get sad and lonely apart. Any advice? They have to be apart until the stitches heal (and big sister is a bit of an aggressive groomer). How can I ease their loneliness? They will be in separate for a week or two.