-No such a requirement. Usually, if a person with AOS stay outside US for a longer time (e.g. > 1 year), USCIS might think this person may have no permanent intent to live in US, and thus, make some trouble in the I-485. But this mostly depends on the individual IO personal judgement, not a law. In your kid's case, I do not think this will be a problem because a small kid always needs her parents to take care.
this is also why the AP only gives one year. But she has been out of this counrty for more than one year. really worry about that.
Thanks again