Junpei didn't really sound like he met her on the test site.
It doesn't really make sense for her to be there anyways. I am pretty sure Uchikoshi is just messing with the questioner, and would be very disappointed if he wasn't.
I actually kind of have a theory on that.
Maybe she went to the past as well, and was able to basically pull a "Dio" and replace someone else this time.