She went on: "I didn't realise how big it was until I saw it in the mirror."
The tattooist who did Julie's design apparently only does the designs as a hobby.
Julie has had to have blood tests to see if she's caught anything from his needles, but won't know the results for three months.
The design cost £40, but it could cost up to £600 for painful laser surgery to have it removed.
The law says people under the age of 18 can only get tattoos for medical reasons.
Even if they have an adult with them, or have permission from a parent or guardian, it's still illegal for anyone to give young people a decorative tattoo.