I disagree with some of this, and I think some of you are applying way too much logic to the concept of "butterflies" and also your reaction to it.
I don't know what study you're citing, but the heart rate of the subjects could be beating fast or slow depending on plenty of variables - nervousness about being in a study, fear of partner leaving, or simply real attraction which can happen well after the honeymoon stage.
Assuming she's being honest, you guys have never gotten nervous or excited around a woman you met or started dating? I understand what she means, I've been there, red pill and all. If you're not feeling that, you're missing out, and I don't see it as a harbinger of a doomed relationship - it can go either way. You're allowed to enjoy these pleasures in life, no matter how juvenile they may seem, as long as you keep your head screwed on straight.
And like I said, her words ultimately don't add up to much anyway, it's her actions that count. For example, if she said it with a smile on her face while she was in your bed taking her clothes off would you bat an eyelash? Doubt it. There's no need to be hamstering this stuff, keep it simple.