My best friend likes my ex. Read entire story. Where do I draw the line?

Me and my boyfriend dated for a month. I ended up breaking up with him because I felt like your relationship was getting boring and we didn't like each other as much as we used to. A couple days before the break up, my best friend hooks up with my boyfriend's best friend. I thought it was a little weird at first, but I got over it. Their relationship only lasted a few days though. After the break ups, my ex would act weird around me and we hardly ever talked. Then over a weekend, both my ex, best friend, and I go to a party. There my friend is flirting with my ex and she starts doing all sorts of things. Midway into the party, she tells me that she likes him. I am speechless. I find out that he likes her back. A couple days later I individually tell both my ex and best friend that I am uncomfortable with them dating. Well, it turns out that they just told me what I wanted to hear. A few days later, she tells me that he asked her out but she told him to wait until next school year. I am totally uncomfortable with the situation and they both know it, yet they choose to just ignore me and have no respect for my feelings. Where should the line be drawn??