There is a mitzva to stand up for a Talmid Chochom. Chazal tell us that Eishes Chaver KiChaver, the wife of a talmid chochom is like a talmid chochom. Is there an obligation to stand up when she comes into a room?
Rav Shmuel Wosner (Shevet HaLevi 10:13:7) says that his question is brought down by many acharonim. He boils it down to three shittos. According to one there is a Mitzvas Aseh to stand up for her Min HaTorah and it is Kavod HaTorah. According to another it is a Mitzva MiDiRabbanan. A third opinion is that it is not a Mitzva but a Midas Chasiddus to stand up. The Chida brings that the Arizal said one should not stand up for the wife of a Talmid Chochom.
If her husband dies, Tosfos seems to say that there is no longer a Mitzva. The Taz brings from the Maharam Mintz that there still is a mitzva to stand for her unless she marries an Am HaAretz.