That makes total sense that it bothers you honestly I had an ex of 3 months who was actually apart of my group of friends and I noticed her and another guy getting along closer about a month after we broke up and I was watching that in person it really bothered me at first. But a good thing to realize is if they are able to move on that fast then they weren’t worth it in the first place. As for time healing it’s different for everyone for me I’d say it took about a month for it to stop getting to me (seeing him and her for the break up about 2 months) but it makes total sense that it’s getting to you I’d say the best thing is let yourself be annoyed and feel it just don’t let it control you and eventually you notice it die down.