I was just wondering if its proper for girls to be master of ceremonies because I heard once that they should not be allowed to become one.
Canon law permits the laity to fulfill liturgical functions if there are no clergy or installed ministers to fulfill the roles:
Can. 230 §2. Lay persons can fulfill the function of lector in liturgical actions by temporary designation. All lay persons can also perform the functions of commentator or cantor, or other functions, according to the norm of law.
In 1994 the Sacred Congregation for Divine Worship and the Discipline of the Sacraments issued a ruling that men and women can equally fulfill the roles foreseen by canon 230 §2 including altar servers. The Congregation noted that while it is permitted for women to fulfill such roles it is still up to the local Ordinary to permit it.
Given that there is nothing essential to the role of MC requiring ordination, and barring a direct statement from an appropriate Congregation against women serving as MC’s, it would appear to indeed be permissible.