Hannah-Marie Clayton objected to the slogan 'Loved by kids, approved by mums' on the boxes of the chocolate flavoured breakfast food, saying it's often her dad James who makes her breakfast as her mum, Anne-Marie, sometimes works away.
The cereal giant replied to her to say they would be altering the wording to 'Loved by kids, approved by parents' and that the boxes will be on supermarket shelves in the near future.
"Also some people don't have a mum and they might find it upsetting."
Hannah-Marie spoke to her parents about the slogan and they told her she could write to the company if she wanted. Her mum then looked up the address and left her daughter to it.
In her letter she wrote: "I feel that quote is sexist, men are also able to make breakfast. My dad does it a lot for me because my mum works away a lot and is not always there for breakfast.
"I would recommend instead of putting 'mums', put parents or carers. It would just mean a small change. In this world today we shouldn't just rely on women."
Hannah-Marie said she was amazed when she received a reply after coming back from holiday. It read: "You recently shared your thoughts around the statement of 'Approved by Mums' on our improved recipe Coco Pops.
"I wanted to let you know that we've recently renewed our research and our new pack design will refer to approval from both mums and dads.
"Apologies for any offence caused and thank you for your feedback, which has played a part in our decision to change."
Anne-Marie, an airline cabin crew leader, said her daughter is always keen to voice her opinions and question why things are done in a certain way.
The slogan change comes after a protest by Fathers4Justice in a Peterborough supermarket earlier this month, over the exclusion of the word 'dads.'
Father of three, Matt O'Connor, founder of the group, went into an Asda store with other dads to protest about the packaging by dumping Coco Pops onto the floor before pouring milk on them.