My girlfriend always hangs out with guys?

ok weve been dating for almost 2 years now im 16 and shes 15, ive tryed to tlk to her and yes she cut it down alot but i still hate it, ive done almost anything i can thi k of, i just tlked to her and she said ahe wont nk more but i dont belive thay at all so im just asking u guys and girls out there , is there anything else i can do(i really like this girl and i dot wanna loose her)