I don't imagine this will get much traction, I just need to vent a little. TL;DR at the bottom.

So basically we broke up in August, which I recognise is quite a while ago now, but I was completely heartbroken and it really sucked. However, we stayed close friends and I still consider her to be one of my favorite people (maybe a little masochistic). Anyway, in October (so not that long after, considering we were dating for over a year and a half), my ex informed me that she planned on starting dating again and I was like, okay, this still sucks but you've got to move on with your life. 
She started seeing this guy, who's super nice and I really like and he makes an effort with me so I'm really supportive of her being happy and I'm glad she's found someone really great, even if it can't be me.
The only problem is that is still really hurts when I see them together, when they're holding hands and giving each other like caring looks, you know, the usual beginning of a relationship stuff. 
Just hanging out together, as a group, I have no problem because he's very easy to get along with. Like I said, I like him as a person, and she's still a really good friend so I feel like a massive asshole being mad at them for expressing their love for each other when I'm around. It's just the cutesy little things that I remember us doing when it was her and me together. It also sucks that I'm now the only single one in our friendship group (that she introduced to me).
I'm afraid of bringing it up to her in case she gets defensive and I seem like I'm being petty and should just get over it. I'm not even sure she realizes it hurts me. But sometimes when we've been hanging out for a while, the jealousy spills out in little nuggets of meanness, and I feel like a class A jerk.
So AITA? Or is it okay for me to be upset with her for being, in my opinion, a little tactless?

TL;DR ex and I broke up in August. I still hang out with her, and her new boyfriend, but sometimes get irrationally angry/jealous when they're being cute together.