She told the court: "He let people cheer him on in matches and he let people call me all the names under the sun."
She later sobbed as she shouted: "I have 100% told the truth about it. He knows for a fact he did it to me. He lied about the others for a year and now he has admitted it.
"I've had thousands of people call me a liar, a slag and a little slut for a year.
"They say I was a silly little girl out to ruin a man's career. Yes, I was a silly little girl but it's not my career being ruined so I shouldn't have been made to think that."
Prosecutors say Johnson and the girl exchanged hundreds of messages via text and social media around the time of their two meetings last year.
During her cross-examination by Johnson's lawyer Orland Pownall QC, the schoolgirl said she found the messages Johnson "creepy".
She said: "Someone texting a 15-year-old girl - they're not completely normal."
She added: "I thought that when I told him my age he would have backed off. Who just asks for a random fan's number?"
The girl was also asked about messages she posted on social media about her meetings with the former Sunderland winger.
Mr Pownall, defending, referred to one Snapchat message, which was later pasted onto Facebook, in which the girl stated: "He's picking me up this week and I'm riding him."
Speaking to court via a video-link, the teenager said: "I was trying to big myself up as any 15-year-old girl would."
The girl wiped away tears as she told the jury she never thought she would end up explaining herself in court.
The teenager later said: "I was trying to brag about it and show off about it. How many teenagers can say that's happened to them?"
The girl told the court: "I thought I was big and I thought I was clever... I feel so stupid now for not seeing but I didn't see it at the time."
It emerged yesterday that the girl did not mention some of the more serious activity in an initial police interview and later said she had held back from describing some of what happened to protect Johnson.
Mr Pownall asked her today whether she was still trying to protect the 28-year-old.
The girl became tearful as she said: "No, because he did nothing to protect me and he made me out to be a liar."
Later in the cross-examination, the girl got more upset and continued to insist she hadn't wanted to get Johnson into trouble.
She said: "I didn't want that to happen to him. I saw myself as playing a part in it as well, I thought I'd done wrong too."
The girl began sobbing again and asked for a break.
Johnson's girlfriend Stacey Flounders, who was absent from court yesterday, was at his side again today as he entered Bradford Crown Court.
Yesterday, the jury was played two video recordings of police interviewing the girl about her relationship with the footballer.
In the first interview, the girl explained how she first met up with Johnson - who she said she idolised - on January 17 last year and he signed two Sunderland shirts for her.
She described how Johnson exchanged WhatsApp messages with her after their first meeting, saying 'you owe me for this' and "am I going to get a thank you kiss?".
She said that, on a second meeting with the player, they started kissing and then: "He undid the button on my trousers... he got his hand down my trousers. He started to put his hands in my knickers."
The teenager told the officer that Johnson knew how old she was and added: "He asked me when I was 16."
The jury was also played a second police interview during which the teenager described more serious sexual activity, including how she performed a sex act on Johnson during the second meeting in his car.
The woman police officer asked her how she felt. She said: "Not very good. I was disappointed in myself."
When the officer asked her why she did not mention the more serious sexual contact in the first interview, she said she was worried that talking about it "would only make it worse".
The girl began her cross-examination by Mr Pownall yesterday, but broke down in tears after about an hour of questioning.
Before she became upset, the girl told the jury: "I wanted to keep him (Johnson) out of trouble. I didn't want to get him in more trouble than he was."
TEXT MESSAGE TRANSCIPTS: THE JURY HEARD JOHNSON AND THE TEENAGE GIRL EXCHANGED 834 ONLINE MESSAGES DURING A TWO-MONTH PERIOD
He messaged her on WhatsApp in late December 2014 and asked if she believed it was him.
Girl: Still not 100 per cent sure ha ha
Johnson: You sound a bit unsure lol x
Girl: I don't know it's just surreal ha ha
Johnson: Why?
Girl: Like you are my favourite footballer. You could update your Twitter saying Happy New Year and then I'd believe it's you.
(He then sends the requested Tweet)
Girl: Ok I believe you.
Johnson: Lol
(He agrees to sign her club shirt and they chat about plans for New Year's Eve)
Johnson: Where are you going out at?
Girl: ...I'm not old enough to go out
Johnson: Yeah but you look old enough
Girl: No believe me when I say I'm 15
Johnson: Ages then lol
(Later they chat about the girl being shy and her ability to handle alcohol)
Girl: It seems like I'm the only one who can handle vodka
Johnson: Bet you are not shy with vodka
Girl: No not at all
(Later Johnson talks about their meeting)
Johnson: Thought I would get a proper thank you kiss for the shirt
Girl: Didn't ask
Johnson: Well I can come back and get one
Girl: Why didn't you ask us for the thank you kiss?
Johnson: I just didn't think you would have wanted to
Girl: Wouldn't have bothered me
Johnson: You are meant to want to kiss someone
Girl: Well I do want to absolutely
Johnson: Well we need to make it happen then
Girl: And we will then
(Later they continue)
Johnson: Am I only getting a kiss?
Girl: It depends on what else you are after
Johnson: Dunno depends on what you are up for. A little bit more than kissing.
(After their encounter)
Johnson: Think we had better go in the back next time
Girl: Yeah yeah
Johnson: That wasn't convincing
Girl: Sorry my hands are freezing
Johnson: Was worth it though
Girl: Do you think?
Johnson: Do you not?
Girl: Yeah was checking that you did
Johnson: Yeah was class. Just wanted to get your jeans off.
