If someone doesn’t have nightmares or flashbacks about their assault are they lying

If someone got sexually assaulted years ago and says they don’t have nightmares about it would you believe that they got assaulted? I know this one therapist that asked her patient about having nightmares or flashbacks and she said no then her therapist claimed that the girl was lying about the assault and she believe it never happened and was just in the girls head that it happened. When I was talking to the girl about it she told me that she denies going back to the place where the assault happened which I believe speaks enough about the incident.