Ashleigh was given the £25,000 prize by Lord Sugar, who described watching her work on the show as "a great privilege".
The 17-year-old beat Lucy Beauvallet into second place. Ashleigh and Lucy won this week's final sport branding task, knocking out rivals Patrick McDowell and Maria Doran.
Speaking to Digital Spy about her victory, Ashleigh said: "I'd set myself up to come second. Lucy was great throughout the show and she's just as worthy a winner as me.
"I think it was Lord Sugar's instinct in the end. I'm not the usual Apprentice candidate and maybe that was what swayed him to me in the end. I think it really was a 50/50 chance when it came down to that finale in the boardroom."
The student said that she had "grown in confidence" during the series and claimed that "making great friends" was her personal highlight from the experience.
"I wouldn't say [I'm] more determined. Everyone was there for the same reasons. I just think I had a raw edge," she said.
"I've never claimed to be someone that I'm not. I never once made a daft claim, or said, 'I'm fantastic at this', 'I'm the chairman of this'. That definitely worked for me. I just say it as it is."
Joking about her rivals on the show, she commented: "It was definitely an intense experience, but I've worked with people in the big bad world already that I didn't like.
"I worked in a shoe shop with a manager who was really nasty. I'd done all that before and I was ready and prepared for that. Maria was a big character, bloody minded and argumentative, and she'll fight her side until blood is drawn, but deep down she knows when she is wrong and she's not afraid to admit it."
Ashleigh also called for the BBC to back Lord Sugar and give him another series of Young Apprentice, describing the show as "life-changing".
"I'm a normal girl from a normal background and I used to watch this show thinking it was all people from money and people like me didn't get opportunities like this. But I'm proof of the pudding that this show can change people's lives. This show has changed my life," she said.
The previous winners of Young Apprentice are Arjun Rajyagor and Zara Brownless.