“oomis, mikvah and candles become effective for her with marriage, not with bas mitzvah”
The statement made was that girls do not do one single mitzvah more after they turn 12. That statement is erroneous, as I pointed out the muiztvos they are obligated in. And I am sure you would agree that in most cases, this is after they turn 12, though it may be several more years down the line.