I think the only thing consistent is Alice has always been the preferred canon L.I. for the MC, but because at the time when he moved in, she was already dating Leah on the down low he had no choice but to temporarily move on. Since she was already spoken for, he had no choice but to date other girls until strangely enough, she became intrigued with the idea of acquiescing to the desires of the MC and gave him a shot. Now technically you can say she's always been in open relationships since her and Leah weren't public, but even then she cheats on Leah for the MC.
That should have been a big clue monogamy was not something she could 100% commit to and her desires whether out of boredom or lust were always going to lead her astray. Point I'm trying to make is, maybe the MC and us as the players should have not gotten our hopes up for a happy solo ending with her and the MC. While sure, Melody and even Leah were shown in their respective endings that they matured, and grew up and went on with their lives, at least when it came to relationships, that was always going to be a tricky subject with Alice.
While there might have been scenes in the game where she tried to show the same level of love and affection to the MC, like other have pointed out, actions speak louder than words. Hers tells that while she may have meant to convey love for the MC, and maybe in a weird way she does 'love' him, she also loves her open bohemian lifestyle just as much if not more.
Yes the epilogue points out they both carried on with lovers after getting married, but he did not keep a quasi-serious long term relationship with someone while married to her. His preference might have just as easily been just the two of them committed to each other, settling down to have a family and grow old together however since she clearly had no interest in that, if the opportunities presented themselves, I wouldn't blame him for taking the occasional lover either. Again, the difference being they were most likely flings with no real emotional attachment, otherwise what kind of husband would seemingly allow his wife to carryon taking lovers left and right with no established ground rules while he deny himself the same opportunities?
