What is the Islamic ruling if a lady dies, and her children want to build a masjid in her name, does that count as sadaqa jaree an and does she still get hasanaat for the masjed her kids built?

Rasulullah (saw) said, when a person passes away, all his actions terminate but three; knowledge through which people benefit, sadaqa Jaariyya(recurring) and a pious child who makes dua for the parents. Building a musjid on behalf of the mother will certainly be sadaqa Jaariyya as people will perform salaah and other righteous deeds there. Your mother will be rewarded for all that, Insha-Allah.

And Allah Ta'ala knows best

Mufti E. Desai