Just because you haven’t heard about the threats doesn’t mean she’s not been threatened.
That said, here’s the info you requested:
http://conservativefiringline.com/creator-of-melania-ad-alleges-threats-from-trump-supporters/
We have no way of knowing if these are Trump supporters or not. Could be paid George SOros hacks.By all means, however, you are free to believe this woman, just as you believe the lies that come from Ted Cruz’s boogery mouth.