You will need to do an analysis under child Status Protection Act to see what her eligibility to file for an adjustment is. If she is in the U.S. why hasn't she filed for adjustment? Better yet retain an immigration attorney and don't try to represent yourself in a very complicated area of law.
The length of time the visa is being processed should be subtracted from her age under the Child Status Protection Act, so she can preserve her visa category.
The above is intended only as general information, and does not constitute legal advice. You must speak with an attorney to discuss your individual case.
Try to avoid a potential mistake and consult with a local immigration counsel to properly address all your present variables, because even slight immigration mistakes, in my professional opinion, become too costly and, at times, beyond repair.
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