recovering messages from accounts you've been blocked by

recently me and a friend got in a huge fight, she said some threatening things and has continued such things on other platforms aswell, I saved her messages and waited till the next day to see if she would say anything else and she had blocked me before I got the chance to screenshot or take photos of her messages. im scared this is going to get bigger and im going to have to take this to the police but I dont have the records if the photos to show them. is there a way I can email snapchat to get the messages back or get a parent to email about the messages? I dont want to get the police involved to get the messages back yet, and the only policies ive seen are American ones (I live in Australia) any advice is welcome