Grace Mugabe has returned to Zimbabwe after being accused of assaulting a model in a Johannesburg hotel room.
Gabriella Engels, 20, has claimed she was beaten with an extension cord, posting a picture on Twitter showing a gash on her forehead.
She said the Zimbabwean first lady's bodyguards stood by watching.
Police had previously put out a red alert to stop Mrs Mugabe, 52, leaving South Africa.
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But a security source told Reuters on Friday that she had been granted diplomatic immunity.And on Sunday, state media reported that she had arrived in Harare with the 93-year-old President, Robert Mugabe, aboard an Air Zimbabwe plane.
There has been no official comment from Harare on the allegations.