The schoolgirl groomed by Adam Johnson wept in a police interview as she told an officer she felt “compelled” to perform a sex act on the former Sunderland footballer even though she knew it was wrong, a court has heard.

The 15-year-old also broke down under cross-examination on Monday as she claimed she had wanted to protect her idol from police when rumours circulated about their alleged sexual encounter.

In a tearful police interview played to the jury at Bradford crown court, the girl claimed she performed a sex act on Johnson, 28, “because I didn’t know what his reaction would be if I didn’t”.

The teenager – still wearing her school uniform – told the police officer in April last year that Johnson had texted her to say “you owe me for this” after giving her a signed Sunderland football shirt.

The girl, who cannot be named, described how she felt “awkward” when Johnson allegedly kept trying to place her hand on his penis while they kissed in his car.

“He put my hand on his trousers then put my hand back down there [his trousers] so I felt a bit awkward if I pulled my hand back. I just sort of felt compelled to do it in a way because he took his trousers down … It’s hard because I can’t remember how it started – I just tried to forget about it,” she told a detective.

The schoolgirl claimed she performed a sex act on Johnson “for a couple of seconds” before stopping when the footballer allegedly said that if she continued he would “have to have sex” with her.

The girl alleged the sex act was Johnson’s idea “because he sort of put his hand on my back, not forcing but gradually pushing forward a bit”. Asked how she felt after the alleged sex act, the teenager wiped away tears and said: “Not very good. Like … I don’t know. I was disappointed in myself.”

The trial was halted during the girl’s evidence as she wept uncontrollably while explaining how she lied to try to keep Johnson out of trouble. Under cross-examination by Johnson’s counsel, Orlando Pownall QC, she admitted asking friends not to disclose to police that she had performed oral sex on the footballer, the jury heard.

“When the rumours had got round school what had happened with Adam Johnson, not the full story had got out and I wanted to keep him out of trouble,” she said in tears. “I was worried there wasn’t any evidence there on the texts. I was worried people wouldn’t believe me.”

Sobbing, the girl said she was lying “to protect somebody else not protect myself”. She added before breaking down in tears: “At that time I didn’t realise it was wrong and what had gone on was wrong.”

The judge, Anthony Rose, ordered a 10-minute break in proceedings while the girl composed herself.

Rumours about the alleged sexual encounter started circulating among the girl’s schoolfriends just days after her meeting with Johnson, the court heard. Pownall suggested that the girl asked friends to give police a partial picture about what had happened when the rumours “spiralled out of control”.

The girl sobbed: “It was [a] concern because I didn’t want him to lose his career or anything. I wasn’t bothered about myself at all … I was trying to protect him so he didn’t lose everything.”

Earlier, jurors heard the girl’s first police interview in which she described how she felt shocked and worried after allegedly being groped by the footballer. She described how she avoided meeting up again with the then Sunderland player because she “knew it was wrong”. However, she said she was reluctant to go to the police.

Of the alleged sexual activity on 30 January last year, she told the police officer: “I would say I was a bit shocked. As much as I was expecting it to happen I was still shocked it was. I was a bit worried because I knew I had done something wrong. It wasn’t that I didn’t want … it’s just I knew it was wrong. I’m not one for being able to hold guilt.”

The court heard that the girl added: “I didn’t want anything to be done about it – I just wanted to drop it, but my mum said what he’s done is wrong.”

The schoolgirl was interviewed at Durham police station, with the footage shown in court during the second day of the trial.

She claimed the relationship started when she sent a friend request on Facebook to Johnson “who I’ve idolised for a long time so it was surreal”. Johnson accepted her request later the same day, the court heard, and they later exchanged mobile numbers.

The girl told police Johnson knew her age, what school she went to, that she was a Sunderland season-ticket holder and even where she sat at the Stadium of Light, the jury heard.

She described what is alleged to have happened when the two met behind a Chinese takeaway – weeks after he accepted her friend request. “I was kissing him for quite a while. Then he undid my button on my trousers and my zip and it took him quite a while to do that. He put his hand down my trousers and started, like, putting his hands in my knickers,” she claimed.

“That went on for quite a while. Then he stopped for a bit then he put his hand down again. Then he started to put my hand down his trousers, but I put my hand back a bit but then he put my hand back on over this trousers.

“I said ‘haven’t you got to go’ because it was nearly six – it was after the time he said he had to go – and I tried to bring it to an end because it was getting slightly awkward and stuff.”

She described how Johnson sent her further texts on WhatsApp after the alleged sexual encounter, wanting to meet up again.

“He sent me more messages offering to meet up and asked to meet the next day, but I was with friends. It wasn’t that I didn’t want to, but I was a bit hesitant because I knew it was wrong. I just said I was going out for a meal. Then everyone started to find out about it,” the girl told police.

She described how she “broke down” and confided in her parents when schoolfriends learned about her and Johnson. She was taken to a police station by her mother and a family friend, the jury heard.

The court has already heard allegations that Johnson knew the girl was 15 within hours of them exchanging messages on New Year’s Eve 2014. Days after the alleged sexual touching, he is said to have searched the internet for “legal age of consent”.

Johnson denies two counts of sexual activity with a child. He has pleaded guilty to grooming and one count of sexual activity with the 15-year-old.

The trial continues.