I don't know how but you've skipped over scenes, like you've done the affection route ( loaned her money ), and from there you visited her 4 times in her bedroom to try on clothes, then a 5th time where she tells you about the studio, then the next morning you wake up, get a message in bed saying to visit her at the studio then you go to the studio.
But some how, you've skipped the last clothing visit to her bedroom, not got the morning message and now can't access the studio and I really can't see how you've done it, lol.
I really don't think this is a save issue or a game issue, I think it's just the way the games been played, but at the same time it has to be a game issue.
So let me see if i've got this right, you played 0.4 and I assume you did the studio scene where you either spied or walked in or her. then that was the end of her story in 0.4 so now in 0.5 loading in your old save her story isn't continueing for one reason or another.
I'll keep looking into it, see if I can find the issue.