I bought this mare https://horseeden.com/horse.php?id=15062585 and bred her. I was looking at her offspring history and it says that she had already foaled that year. She does not have an extensive breeding history. Could it just be a typo and that her past breeding was done last year?

Odd

Only thing that comes to mind is that she wasn't bred at all in June until it was technically July but before RO occurred at 2:30 AM GT. Meaning she was bred July 1st between 12:00-2:29 AM GT. If that's the case then that would explain it.

It really doesn't matter.. the previous foals are deceased... I just wanted to keep track of what she produces per year and it just seemed odd to have it show july 2018 twice.

AB is probably correct. Since the first July foal is shown as being born on July 1st, and there is no June foal, the baby was likely born just before rollover. The date was technically July 1st, but the game hadn't yet switched from June to July.