I can understand from what phase you going through
I think u should wait until her board exams. Let her concentrate for her exam and not you
If u'll ask her out now or even call her, she will start thinking abt u and less abt her exams
right after exams, call her, exchage emails but dont ask her out right away, lot of things changes in two years, u dont know precisely how her life has been in those past two years
If she still likes u, she will definately chat with u without looking at time zone, if she doesnt she wont waste her time one net chatting to u
I mean its day here nd night there and vice versa, so she wont look at darks nights but at bright chat screen.
She will definately by angry on u, bcoz u left her and came to US (talking from experience, I was not in love but my best friend since UKG but I had not even told her that I was coming to US, started being absent and my aunt told her later)When I started talking to her after a year, she was upset, which was justified,)