In an interview with You magazine, the 26-year-old said that she'd bumped into a former classmate during a trip to her local supermarket.
'She came up to me all smiling and friendly and told me her two little girls thought she was the coolest mum because we'd been friends at school,' the Gogglebox star told the mag.
'Usually I'd just smile and walk away. But I had this memory of her coming into school and wearing fake teeth after I’d had my bike accident and doing a really horrid impression of me.'
She added that although she'd laughed along at the time, she'd spent the night crying in her bedroom.
'When she used the F-word – the "friend" word – I shook. I told her that we’d never been friends and that she’d been a bully who had destroyed my confidence and ruined my time at school.'
'I told her I hoped her two daughters would never go through what I'd gone through or have to deal with anyone like her'.
It's the first time Scarlett has opened up about her childhood bullying ordeal.
Speaking to The Sun after her appearance on I'm a Celebrity... Get Me Out of Here in 2016, she explained how she would be allowed to leave school ten minutes early 'so I didn’t get beat up'.
'I would just walk around Asda’s car park until three o’clock or up until the time I was meant to come home,' she said. 'I just felt so embarrassed to tell my mum and dad'.
'I would pretend to my parents that I loved school. Sometimes I would sit in the toilets at breaks just so I didn’t have to wander around the playgrounds on my own.'
She added that an accident which caused her to have plastic caps on her teeth and left her with Bell's Palsy, meaning that the left side of her face drooped, made the situation worse.
'I smashed my teeth and had all the nerves taken out, so I had a black tooth as well as a monobrow, and I was a little bit chubby, and then half my face was on the slide.
'There was just loads of things. One of the kids also saw me metal detecting with my dad, so you can imagine how that went down.'
'I mean, it's funny now. Jesus, it wasn't funny when I was going into school. It’s worked out well now, it's built character.'
'I tried to fit in but failed miserably, so I just carried on being me as my dad said, "Just be you, just be yourself".'
Before her departure for the outback, Scarlett told The Sun's TV magazine that she was 'not like other kids'.
'I think it was the monobrow, and teeth that could chew an apple through a letterbox,' she joked.
'I was a bit weird. Even as a kid when I was 11 or 12, I would watch shows like Bottom, The Young Ones and Red Dwarf.'
'I was really ugly, I was really weird and I believed in aliens. Even as a kid when I was 11 or 12, I wasn’t like the other kids in the school – I still wore my hair in pigtails. No wonder I got picked on.'
Scarlett said the bullying went on until around Year 9, when she switched schools and made some changes to her image.
'Puberty hit over the six-weeks holiday, all of a sudden I got boobs, my mam let me wax my eyebrows and I went and got my hair done. I just had this new-found confidence. I thought: I'm gonna go to this new school and I’m just gonna be me.'
'I still didn't try to fit in but, luckily, everyone was nicer there. You can't please everyone all the time. It's best just to be you.'
Now in the public eye, and having recently lost over three stone in weight, Scarlett added that she has to keep up this philosophy of self-confidence when nasty comments pop up online.
'Although it's 2016, men still think they can form an opinion based on what women look like. I'll be honest, sometimes it does hurt when they say stuff. When you get it a lot, it's impossible to say that it doesn't bother you. I have learnt to never read the comments on websites,' she concluded.
'Being bullied made me realise that people will like you or not like you anyway, so you might as well be yourself and say exactly what you think.'