So cute!
If your friend is right, and you have an even split (four males and four females), I would recommend keeping two of the female babies rather than just one. If you only keep one, it means you either have to find a home willing to take all three of the other girls, or find a home for the lone female that already has a female rat, but even then, it will be a while before she is big enough to introduce to the adult. It would, in my opinion at least, be better to keep her with her mother and sister than to send her to a home where she'll be alone for a couple of months.