President Mugabe has vowed to stand again in the election, but Grace could run if he dies before the vote.
Grace Mugabe, who was appointed leader of ZANU-PF’s women’s wing in a surprise move two years ago, is well known for her fiery speeches and verbal attacks on opponents.
In 2015, she led a campaign which led to the ousting of Deputy President Joice Mujuru.
President Mugabe, the world’s oldest national leader, turns 93 on Tuesday, with a celebration party planned for next Saturday.
Grace has previously pledged to push Mugabe in his wheelchair to election rallies if needed.
Mugabe, who has been in power since Zimbabwe’s independence in 1980, has avoided naming a successor and his party is divided between factions jostling to succeed him.
Grace bemoaned the infighting, telling those seeking to succeed her husband: “Let’s not fool each other, let’s wait for God’s time.”