I wana breakup,but dont wana hurt her...its all online(GALS PLZZZ need ur help,sugest me)..?

few months bak i met a gal from US online..n today she loves me like (more than herself),even ready to quit her country for me,in case m not able to make to US...I KNOW its not possible to spend life wid her,how to tell her that "our frndship which converted to online love cannot end up in marriage"..i know she will b badly hurt,bt i need to say soo so that she doest just waits for me n ruin her life...how to break up??i m fixed,thinkin its solution...