Police said the incident took place on December 25 when the woman, who works with a travel agency, and her male friend went to Buddha Garden.
"When the woman, along with her friend, was leaving the Garden, two men suddenly stopped them and asked the time-table of the Garden," said a senior police officer.
The woman alleged that after introducing as a police personnel, one of the accused sought Rs 200 from them.
The woman also claimed that the two accused molested her and extorted Rs 200.
The officer said police have arrested one accused, identified as Sandeep Singh, a resident of Rohini, while his accomplice would be arrested soon.
A case of molestation and extortion has been registered against them and further investigation is on.