"Happy massacre," Fatima Naoot wrote on her Facebook page in October during Eid al-Adha, the Muslim feast of sacrifice.
Animals are slaughtered during Eid to commemorate the willingness of Abraham to fulfil God's command to sacrifice his own son, although in the end God provided him with a sheep.
Naoot, who is Muslim, deleted her posts from Facebook after controversy erupted about them.
But a judicial official said yesterday that she admitted during questioning that she had written them.
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"It is the price paid by those who carry torches of enlightenment at every age," Naoot wrote on Friday after having been informed of her trial which is due to start on January 28.
She said that in October she had posted messages on Facebook to congratulate Muslims for Eid al-Adha but "urged them to respect the offering and not humiliate it by flooding the ground with animal blood".
Egypt's constitution outlaws insults against the three monotheist religions recognised by the state - Islam, Christianity and Judaism.
In June, in a separate case a Coptic Christian man was sentenced to six years in jail for insulting Islam.