The woman said the actor groped her in a room at Granada Studios in Manchester after being led past the Rovers Return pub.
Last week, Preston Crown Court heard she thought she was about 14 when Mr Roache, who plays Ken Barlow in the TV soap, arranged studio passes for her and her younger sister.
The court heard that the alleged victim and her sister would sit on the steps outside the studio in the summer holidays in the mid to late 1960s, along with other girls and boys who were autograph hunting.
It is alleged Mr Roache, who plays Ken Barlow, took her into a dressing room and indecently assaulted her. Louise Blackwell QC, for Mr Roache, asked if she was telling the truth. The woman replied: "Why the hell would I put myself through all of this?"
Mr Roache was charged last May with two counts of rape on an alleged victim, and subsequent publicity led to four other complainants coming forward.
The witness said she felt the incident had been her fault "for being there in the first place".
Her sister claimed that she was abused by Mr Roache on a separate occasion.
Mr Roache, 81, of Wilmslow, Cheshire, denies two counts of rapes and five counts of indecent assault involving five complainants aged 16. The trial continues.