Send it a day after she qualifies.
NOA1 has been taking 2-4 weeks recently, and it will extend her GC by 48 months.
You should wait for the biometrics appointment letter. If they re-use old biometrics, then you are golden. If not, then I suggest you wait and attend the bio appointment, unless she will return by that date. Bio appointments are around 6-8 weeks from filing, depending on work load of your local USCIS office.