While her partner's commitment to proposed legislation allowing same-sex marriages has been questioned in recent weeks, Trierweiler revealed she had accepted an invitation to participate in the wedding of gay friends.
"I'm delighted that I'm going to be a witness at one of the very first marriages for all," Trierweiler said.
A law providing for same sex couples to wed and adopt children is expected to be on the statute book by the middle of next year.
Its passage through parliament is likely to be stormy however given strong opposition from sections of the opposition right, Catholic bishops and other religious leaders.
Hollande attempted to take some heat out of the debate last month by announcing that mayors would not be obliged to preside individually over gay marriages if they did not agree with them on principle.
That prompted allegations of "treachery" from France's main gay lobby, which accused the president of legitimizing homophobia.
Tens of thousands of protestors took to the streets of Paris last month in opposition to the government's plans but opinion polls suggest most voters support the planned reform.
Representatives of the main parties in parliament agreed Tuesday that the main debate on the draft legislation will take place in the first week of February.