Payam Derafshan published an open letter to the head of Iran's judiciary, Ebrahim Reisei, in a plea for clemency for his client.
Khishvand, who is famous for her radical appearance and cosmetic surgery, was arrested in October 2019, accused of promoting violence, illicit education, blasphemy, insulting the Islamic veil, spreading hatred and encouraging youth to commit corruption.
Her attorney asked Reisei to take "appropriate and responsible measures within the frameworks of law and issued regulations."
He also quoted an Arabic proverb: "The human who has no mercy, he does not receive mercy."
CNN has contacted Derafshan for further comment.
The lawyer previously told the Center for Human Rights in Iran (CHRI) that Khishvand is on a ventilator at Sina Hospital in Tehran after contracting Covid-19 in state custody.
The judge rejected numerous requests to release her under the amnesty granted to other prisoners during the Covid outbreak, Derafshan reportedly told CHRI.
Khishvand regularly posted pictures of herself on Instagram. Many believe she made herself up to look like a zombie version of the actress Angelina Jolie, with sunken cheeks, an exaggeratedly upturned nose and extra-large pouty lips.
She says she digitally enhances the pictures, but denies trying to look like Jolie.
Iran has struggled with the worst coronavirus outbreak in the Middle East, with more than 79,000 cases and over 4,900 deaths, according to figures from Johns Hopkins University.
Officials in Tehran have accused the US of crippling its medical system amid the pandemic, due to continued economic sanctions.
CNN's Mostafa Salem and Sara Mazloumsaki contributed to this report.