"Security was left with no other option but to remove Engels from the hotel suite."
AfriForum, a civil society group acting on Engels's behalf, denied the accusations.
"Gabriella never attacked Grace Mugabe in any way," AfriForum said.
"It is clear that Grace Mugabe is desperately trying to escape responsibility for her own violent behaviour by using lies to falsely portray the victim as the perpetrator."
South Africa granted Grace Mugabe diplomatic immunity, allowing her to evade assault charges, although Engels and AfriForum have challenged the decision, saying she was not in South Africa on official business.