Confused feelings...?

My friend had a relationship with a guy named Mark that lasted for almost two years. They were so in love until they broke up and were apart from each other over 9 months. During the 9 months she met a new person, Joe. Joe and my friend decided to start a new relationship since she thought it was time for her to move on, but in the meantime she still had some type of connection with her ex, Mark. This bothered her current boyfriend, Joe; She really wanted to be with him but she couldn't stop talking or communicating with Mark, Mark was always there, in her life she couldn't let him go, he meant a lot to her still. And while Mark and my friend were just good friends during the 9 months they weren't together, she always wanted him to ask her out again, always. And now that he did, she said yes with excitement, but now she feels bad for Joe because she's still with him and they dated for 8 months, she cant let him go either, he means everything to her, he's so romantic all the time. She cries every night trying to figure out what to do with her life, she loves Joe, but she also loves Mark. How to get rid of this confusion...