How can i fix my jealousy problem?

ok so one of my friends is what you call.. ignorant. for some reason she always sticks in my head as a girl who tried to steal a guy froma nother girl. so a long time ago she was ahnging with my bf. now i wouldnt mind it if she did nto stay there until 2, said he smelled nice, told me they were alone, and then when me n my bf broke up she didnt even comfort me. n she said to me its not my fault u messed up i told u not to. now i do like this guy carlos ive known him fro 3 years n my bff notices it but this girl doesnt. she says she doesnt but idk if she does, n they're gonna be alone tomorrow n i cant go so they will be alone. n it bugs me that they will. i just cant trust her idk why my head is an rollercoaster right now please explain it to me. i do get jealous easily but not really with my clsoest friends but with friends who are not that close. n her i just dont trust. is there any way i can control my jealousy problem?