Is it Sunnah to put henna on the hands of the deceased, close her hands, and bury her thus? And is there any evidence for that?

There is no evidence in the Sunnah indicating the application of henna to the hands of a deceased or dying woman. The belief that this act is a Sunnah by which one draws closer to Allah, without evidence, is an innovation and is not permissible. Sheikh Ibn Baz was asked about this and replied, "I do not know of any origin for this." Similarly, the Permanent Committee for Issuing Fatwas was asked and replied that the Sunnah indicates washing the deceased with water and lote leaves and placing perfume (hanut) in the shroud. As for placing henna with the deceased in the grave, we do not know of any basis for it in the purified Sharia; rather, it is obligatory to abandon it.