It is Mustahabb (commendable) for females to circumcise. It is narrated
in an authentic Hadith quoted from Abu Dawood Shareef that during the
Prophet (Sallallaahu ?layhi Wasallam)'s time there was a woman in Madinah
who used to perform circumsicion for women (Fathul Bari vol. 16 p. 353)



"Ibn Qudamah (may Allah have mercy on him) said, in his book al-Mughni: "Circumcision is obligatory for men, and it is an honour for women, but it is not obligatory for them. This is the opinion of many scholars. (Imam) Ahmad said: For men it is more strictly required, but for women it is less strictly required." (al-Mughni 1/70).

Circumcision of the female consists of the removal of a part of the clitoris, which is situated above the opening of the urethra. The Sunnah is not to remove all of it, but only a part. (al-Mawsu‘ah al-Fiqhiyyah 19/28).