The magazine claims the recording is part of a video leaked to the publication. YOU magazine quoted Amor as saying the recording was "manipulated".
"They want to inflict optimal damage. It’s an effort to destroy me. They want me to lose everything I’ve worked and fought for my entire life in an instant."
Amor and the Van der Westhuizen family have been involved in legal battles over the Springbok rugby player's estate after his brother, Pieter, revealed the existence of a second will.
The will, which was not signed by Joost, left Amor with "very little". The Van der Westhuizens eventually conceded and said they would not take the matter further, meaning Joost's original will, from which Amor benefited significantly more, came into effect.
Amor told the publication her lawyer was made aware of the tape after Pieter passed it on. “He alleges someone had sent him the video and he simply wanted to inform Sean of its existence."
"We invite the owner of the original telephone conversation to present it to us so we can investigate the contents," Hefferman told TshisaLIVE.
The Van der Westhuizen family told TshisaLIVE they wished Amor well.
"The family has said on a number of occasions that they will not enter into a media circus on matters surrounding Amor. As such they will not comment on the recording. They wish Amor well in what must be a difficult time," said spokesperson Odette Schwegler.