Didn't play the recent update yet but, with how close Alex and Isa have become, I think that too much attention is being given to preparing the throuple, while cutting any of the girls out for a solo relationship a player might desire is gonna be too painful.
Like, personally I rejected Alex (breaking up is always a pain for me, even in games, but Alex is a tomboy, and tomboy = friendzone for me) and was originally going to pursue Isa. However, with Alex constantly being around and being somewhat insecure about Isa being hotter and richer I think I'm better off having the MC leave the girls to their own devices and try for a relationship with Val. I mean, if I went for a solo Isa route Alex would probably feel abandoned from the trio and say something along the lines of, "You gave the special connection we had away for tits and hype, AND made sure to parade your new GF around me! What kind of monster are you?!". She wouldn't be exactly wrong. Also, that sister of hers would probably tell her a ton about how she was right and Alex herself was wrong about the MC. While I don't want Alex as a LI, I don't hate her and don't wanna inflict something like that on her.
Now, if I were an Alex fan, I would probably be a bit wary of Isa too. I mean, I can only have sparse alone time with my girl in the rare moments when Isa isn't around, damn!
All in all, Val is probably the best option for me as I want the MC to be alone with the chosen LI at the early stages of building a new relationship, when that "special connection" is really brittle, and not to twist Alex's wounds by showing her the new relationship of the guy who rejected her (and not the other way around).
Basically, it's the same situation I had in Alive, where I felt that the MC wasn't yet close enough with Nikki to compete with her best friend Erin for her attention and swapped my choice to Mary, whose own best friend Stacey gave her more space.