Is it wise to reach out to ex friend?

I am in a happy relationship and have a small circle of friends and life is overall thriving. A few years ago I was in a long term relationship with my now ex and through our social group met a girl same age as myself. I didn’t really like her at first impression but my partner at the time got on really well with her and they quickly became friends. After a couple of months and seeing her regularly due to our group of friends I too started to become friends with her, we had a ridiculous amount in common and quite quickly we became very close friends, message each other every day and just had the same goals/thoughts etc. (My friendships have never been as close as this one was before meeting her and since) I found out my ex was messaging her things he shouldn’t have been and we broke up soon after, (I have to add before this girl came into our lives we had outgrown each other so the breakup was long overdue) The girl said to me she just wanted us all to be friends and that’s it, although I didn’t understand why she would still message him back (even platonically) knowing he fancied her. At the time I was angry at both of them and didn’t want to speak to them as blamed her for all of it. After a lot of space, I knew the relationship ending was for the best regardless of if the girl was involved or not and it was the best thing to happen to me. Due to us all being in the same social circle I started to slowly talk to both my ex and the girl again and we actually all became good friends and I said to both of them if they did like each other I wouldn’t be bothered if they went out. They eventually did get together but a very very unpleasant situation happened between them (they removed each other completely) and they both wanted me to take a side. I didn’t know who to believe and due to the seriousness of their situation and not wanting to get involved I cut both of them off. My problem now is, even after 3 years I do miss the girl I was friends with and wonder how she is often. I haven’t had any friendships or met anyone that is on the same wavelength as me and I have thought countless times of reaching out and trying to reconnect. I don’t know if it’s a wise move to make? What would you do? Please let me know your thoughts or similar experiences and how they turned out

Only if they're no longer involved with each other. Otherwise, it will just be drama.