"Agarwal has tendered her resignation," according to the office of chairman Ramesh Yadav.
"I had been party MLC twice due to Netaji (Mulayam Singh Yadav). As he is not active in the party, I have resigned. I don't have problems with anyone in the party and I respect everyone. I felt awkward after split in the party and I did not feel like working in it," Agarwal, whose tenure was to end in 2021, told reporters after her resignation.
During BJP President Amit Shah's visit to the state capital last week, two SP and one BSP MLCs had resigned and joined the BJP.
Three sitting MLCs Bukkal Nawab and Yashwant Singh (both Samajwadi Party) and Thakur Jaiveer Singh (BSP) had resigned from the membership of the House.
Sarojini joined the BJP in presence of minister Rita Bahuguna Joshi and Mahendra Singh.
"The joining shows increasing trust and confidence of not only the common man but leaders of the other parties in Prime Minister Narendra Modi and our national president Amit Shah," BJP spokesman Shalabh Mani Tripathi said.