Police in Muzaffargarh city claim Asiya Bibi had intended the deadly substance for her husband, and mixed it with his milk last week - but he did not drink it.
Instead it was turned into a batch of lassi, a yogurt drink, and served to his extended family.
Police said 15 people died and 14 others have been hospitalised, Geo TV reported.
The death toll has been rising since last Thursday, when the tainted drinks were first served and eight people initially died, the report said.
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The local media say the bride had tried unsuccessfully to flee her marital home and return to her parents.
Senior police official Owais Ahmad confirmed that Asiya Bibi has been charged with murder. A man alleged to be her lover, and his aunt, have also been arrested.
The suspect denied all of the allegations leveled against her when the accused was presented before the media.
The three suspects were later presented before the Anti- Terrorism Court in Dera Ghazi Khan and sent into police custody on a 14-day physical remand, the report said.
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