The ward's councillor post fell vacant after the death of Awami League supporter Nazrul in April.
After presiding officers of all polling centres finished counting votes, district's election officer Md Tarifuzzaman announced the results on Saturday evening.
According to the unofficial results, Beauty with poll logo 'lion' bagged 5,266 votes and her rival Iqbal Hossain running with ‘apple’ secured 1,958 votes.
Another candidate Masum Rana got only 687 votes.
Iqbal is the joint secretary of the BNP's Siddhirganj unit.
In an immediate reaction, an emotionally charged Beauty told reporters, "This is the people's victory, this is my husband Nazrul Islam's victory."
"My husband always worked for the people. The way he stood by them during their sorrow and grief, I'll do the same."
She pledged to finish her husband's unfinished job.
"I will also continue with the movement to ensure that justice is served with regard to the seven murders," she said.
Of the total 16, 729 voters, 7,956 cast their vote on Saturday. Forty-four of them were cancelled and eight ballot papers were missing, election officials said.
During the balloting that started from 8am and ended at 4pm, there were no reports of trouble.
Md Tarifuzzaman said the polls were free and fair amid heavy presence of personnel from BGB, RAB and police.
Narayanganj City Corporation's Ward No 2 comprises Siddhirganj's Mijmiji, Painadi, Mouchak, Natun Moholla, Abdul Ali Pool, Hirajhil, Mujibbagh and Mitali Market areas.
The schedule for this ward's councillor election was announced on July 14, after Awami League supporter Nazrul's death.