Basically I work at a modeling agency, and sometimes we need to chaperone underage models on trips. In November, I had to accompany my boss (who is the director of the agency) and I am her personal assistant. On that trip I had to stay a few more days with one of the models because he was 16, and his uncle had to go back to the country, as well as my boss. I was quite responsible with him, and did a good job. Last week I was not at work (due to school, I am an intern) and I was first option to go with the kid to London, because his mom requested me to and that I already knew him and the whole team for the client he was working for. However, while I was gone for the week my boss was about to call me, but a coworker who I was shocked was shady, mentioned to her I will be at school next week (which isn't true, I am doing a work study thing and only had a full week of class that week) and convinced her he should go, not even calling me to check if I could do it or not. When he mentioned to me he was going and he took my place, I was absolutely FURIOUS, because I worked super hard as an intern to take more responsibility and try to get hired full time afterwards. When I confronted him the day he was supposed to leave, I told him he was sneaky and very rude for what he did, especially since I wanted to prove myself to my boss and I wanted to go on her behalf and represent her since I was her personal assistant, his excuse was that she didn't mention it to him. Of course, that is a lie because he backtracked, while a couple of days prior he said he took my place and I was first option to go. My boss found out about the confrontation because another coworker mentioned it, and I told her I was free to go and I told my coworker he should call me next time to double check because its super rude and manipulative. I am afraid now I missed my chance to prove myself, also the fact that this kid is most likely going to travel a lot due to his work with this major client, but my coworker might be the one to go instead of me. I have thought about quitting but don't know if I should bite the bullet and do it.