According to Katie, Danny served has already served five years for offences that include: "Armed robbery, possession of a firearm and possession of controlled substances".
Unfortunately their plans of being together in the outsie world will have to wait another three years as he still has time to serve.
Katie documented her journey from long-distance relationship to meeting her love behind bars.
"I wrote to a prisoner and accidentally fell in love."
In one video Katie shows the letters they've sent each other.
Katie said: "He got my birthday tattooed on his ring finger."
In another of Katie's videos, we see her getting ready for her first in-person visit with Danny, which she described as "the best day EVER".
The TikTok page also shows Katie visiting the jail for the first time, where she looked overjoyed at meeting her boyfriend for the first time.
Katie opened up on her prison visit and said: "I was very, very, very nervous and anxious the whole drive there.
"I couldn't breathe, I felt a bit sick. I didn't know fully what to expect when I got there.
"I had to go through a metal detector, I had to change my top but I expected that anyway. This person came up behind me and it was Danny. It scared the life out of me.
"Obviously I hugged him, we were hugging for ages. I thought I would cry but to be honest with you I was so happy I was just so excited.
"We had four and a half hours for our visit. We had loads of snacks out of the vending machines, which was really nice.