Student Exchange Programs

next week,i’ll leave my school.because my student exchange program is over.so me and this girl have been soo close like a couple but not yet a couple.she really knows that i like her so much,and so does she.but until 3 months,i still didnt told her officially that i want her to be my gf.because im goin to leave her.and her bestest friend told me she is so upset and confused about me(she saw flirted with other girl….how could i find its so hard to told her that i really want her?help me guys