My friend likes my ex, knows I have feelings for him, is it wrong that I'm mad?

So, my "friend" since Kindergarten decided to take pictures of my ex boyfriend and her holding hands him being shirtless, and the caption was "<3 my soulmate" but they're not dating. So, she told my best friend that she liked him, and she told her that that's not really cool since I like him. I know, we sound like fifth graders, I apoligize. But, I told her it was fine I guess since she can't control it. Did I let her off too easily? Or did I do the right thing by letting her get away with taking pictures with him, and announcing to everyone that they were "soulmates". By the way... We broke up a month or two ago, after a six month relationship. Since it was a long time ago, should I let it go?