There was some sort of ritual where young women were invited to spend a night at the temple, with priests. Due to the religious nature of this, they were still considered to be virgins (“marriable” I guess?) afterwards. Quite the opposite, it was seen as an honour. Even if they got pregnant.

I don’t think there’s any evidence of this.

The Bible has a story with a character pretending to be a temple prostitute to secure her inheritance. But when she becomes pregnant, she is supposed to be put to death. I don’t think temple prostitution was at all a thing by 700 BCE, much less 3 BCE, and it seems more like a holdover from extremely uncomfortable ancient at the time of writing practices - kinda like some of the remnants of child sacrifice that you can find in the OT. I think this is also something the Romans would have noted.

This is something I would believe about a Roman temple maaaaaaaybe. I think your source heard a garbled version of the idea of the Vestal Virgins, and got really confused beyond that.