Either way works:D Either this was a bit of a slip up communication wise or this is a "normal" Wanda freakout that tends to happen at least half the time.
Lemme think... Jean and Irene have been there forever so they probably both remember Pietro from the early days, though they would have been a bit older. Irene, being the school psychiatrist, has obviously spent a lot of off screen time with Wanda and therefore probably, by extension, with Pietro. Jean has Sage's powers so she's incredibly interested in what makes peoples' mutations tick and Pietro definitely has an interesting one so there's likely something there. I also don't know under what circumstances Tabby and Pietro would meet but if Pietro has a crazy/wild/doing stupid shit mindset anywhere in there Tabby has probably tried to exploit that.