Lal had a minor argument with Baldev when they met at a condolence meeting for Vilasrao Deshmukh last evening, but the matter appeared to have been resolved.
Baldev's son Siddharth, however, allegedly went to Lal's Oshiwara residence this morning and threatened to kill her, police said, adding they have registered a non-cognisable offence against Siddharth.