Q: Restoring After Downgrade

Hello everyone, my girlfriend and I both had the ios 10 public beta. She started having issues with the messages app where it could not open. So we downgraded back to 9.3.2 or 9.3 I cant remember it was 8 hours ago we did this. We then tried restoring her phone from a back up in iTunes we created on 9.3.2 on the 7th just before we installed the beta but she keeps receiving an error message. I cant remember the exact message but it says that there is not enough space on her MAC to make the backup, even though we are trying to restore.

She has over 400GB of free space on her mac and 55gb on her iphone 6s. Music syncing is disabled as well so the space would be saved.

Is there anything else we can do? I found copytrans shelbee which we will be giving a try but is there anything we can do with apple?