The incident happened in Riversley Park.
Police are appealing for any witnesses to come forward.
It happened at around 8:40am on Tuesday 20th April.
Inspector Gareth Unett said: “I am appealing to anyone who was in the area at the time and can help identify the man involved to contact police. We believe he may have exposed himself to someone else and we’re keen to identify this person.
“These types of offences can be extremely distressing for victims and we will be carrying out a thorough investigation to identify the person responsible. We have also had an increased policing presence in the area to provide reassurance.
"Officers have spoken to the victim to offer her support and will be keeping her updated with the progress of the investigation.”
Anyone who can assist police is asked to contact 101 quoting incident 135 of 20 April 2021.
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