In August, the 22-year-old announced that she was leaving the series for the second time in three years.
Speaking to TV Week, she said: "It was a big decision, but it was time. I'm really happy I came back.
"I like how the character's been resolved and the way she's grown up - she was a little girl when she first arrived and now she's not only divorced but even had a storyline where she needed money and started working as an escort!
"I started playing Kirsty when I was 13. I turn 23 this month, so it's been a long journey for me."
The actress said that she would like to work in theatre in the future. When asked if she would ever return to Home and Away, she replied: "I don't think so, but who knows?"
Hayes's final scenes will go to air in Australia next week.