Fred actually winced at the question; how do you tell someone that he/she is fictional? Actually how do you do it without thinking you are slightly fictional? The brainy female wasn't sure she was ready for this line of thought, but she'd muster through it.
"Uhm, well, Pietro, no. I haven't met them. Truth is, if you're who I think you are, I'm not sure I'd wanna meet you. Don't get me wrong; having Magneto as a father could make anyone into a bad guy. But, uhm, you see, if you're Quicksilver, I can't think of too many times you've been a good guy. Sure, there are other dimensions you might be, think I read of one that you may have been. But, I can't remember. I sorta haven't read comics in a while." It was rather off the cuff, then her eyes went big.
"Oh, oh, I'm sorry. I didn't mean to just let it slide out like that, but...it's hard to tell someone that, you know?"