The Zohar which discusses the seudas bar mitzvah of Rabbi Shimon Bar Yochai would lechora apply to bas mitzvahs (and, to a lesser extent, tzitzis parties) as well. However, what gets lost is the PURPOSE of the celebration, which is to celebrate the person’s obligation in the Torah, not a “rite of passage”.
Why don’t people make a “bar onshin” party at 20?