Is it possible to get over someone without closure?

I’ve been dating Matt for over two years now. We live together and I am deeply in love with him.

He has a female online friend he has known for a very long time, since he was a young teenager I think. She lives in South America. They met once when he was in college, before I knew him well. They had their one perfect night together and then she flew home. They were still in contact when I started dating him but I was under the impression they had fallen out awhile back and weren’t talking anymore.

I learned last night via a violation of his privacy that they rekindled about four months ago and have been speaking fairly intimately ever since. I am not defending my actions as I know they were wrong. I’m not here to talk about that.

We talked through it last night and I think we’re going to get through it but he said the tough thing with her is they never got closure so of course now and forever he will have to wonder what could have happened if she didn’t live so far away. I have asked him to cut off contact with her. I will never try to control who he is friends with but they are obviously more than friends.

I am deeply in love with this man. What I fear now is my own insecurity. I don’t know how I will stop wondering if he’s still wondering about her and what could have been. Do you think it’s even possible for him to stop wondering about her when he has no closure?

I know she isn’t perfect because she is a human. If he were to spend significant time with her he would learn all her bad habits just as he knows mine so well after living with me for almost a year. But he will never spend time with her. He will only have his memories of the one perfect night they shared.

Like all relationship questions I understand I will only get real answers by communicating with Matt. But I trust my jelly friends and want to know your thoughts. Thank you.