All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger.
First of all, you should know that the ‘Aqeeqah is not an obligation according to the view of the majority of the scholars among whom are the Imaams of the Four Schools of jurisprudence; rather, it is a confirmed Sunnah.
The Sunnah is to slaughter two sheep for a boy and one sheep for a girl as we clarified in Fataawa 87342 and 81462.
Slaughtering one sheep for the ‘Aqeeqah of a girl is what is mentioned in the Sunnah, so, if we suppose that two sheep are slaughtered, the Sunnah is still achieved with one sheep and the second sheep is something extra and this is permissible.
Allaah Knows best.