How do you deal with jealousy?

Hey everyone, I am 24 y/o and I have been in a relationship with my boyfriend for 2 years. Lately, I have been feeling jealous of a certain girl that is friends with my boyfriend, even though I know that I can trust my boyfriend and that the girl does not have any romantic interests towards my him. I am generally a rational person, and we talked about these feelings that I am having. But everytime I see them together, there would be an immediate pang in my heart that I could bug me for hours. I know that jealousy comes from the fear of losing someone, and that what makes you feel jealous often reveals your deepest insecurities and desires. I know that I should accept the fact that my boyfriend have female friends, but I often cannot help but feel "territorial" everytime I see him around other attractive female. I am ashamed of having these feelings and my boyfriend does not know what else to say that could help make me feel better. 
I wonder if any of you girls have similar stories on jealousy. If you do, it would be nice if you can share yours too! What would you usually do when you feel jealous? Why do you think you feel a certain way?
Looking forward to your stories! 😆