The incident happened in Kalyanpuri area here yesterday when the woman, a post-graduate, was set to marry one Kamal from her locality.
But as soon as wedding ceremony began, the woman's friends noticed that Kamal was not behaving normally, and informed her, police said.
Following this, the bride herself saw her prospective groom and refused to marry him as she found him mentally unstable, they said, adding that she refused to relent even when her family members tried to convince her.
No case was registered, police said.