I'd say that by the time Akira had that candid little talk with Hisao, Lilly must have already known that Hisao loved her back. He told her he loved her during her confession. He slept with her several times, despite the strain it could place on his heart. He went on dates with her. And most of all, he opened up to Lilly about his past life and the whole thing with Iwanako, which was a really big thing for him. And he opened up to a degree you didn't see on any of the other routes. If she still wasn't convinced that Hisao loved her, what could he have said that made it definite for her? A proposal? They're high school kids.Well, that's what I was talking about when I said "cut off". Not cut her family off from herself entirely, just cut off the prospect of complying with their summons, which is what would compete with their relationship. Meaning make the decision to stay for him before even knowing if he loved her back.
Not to mention there wasn't a lot of opportunity. There were like two days between Lilly coming back to Japan and her confessing to Hisao and a lot of that time was spent travelling, getting settled at the summer home and sleeping off the jet lag/exhaustion from the trip.But the way you phrased that is interesting: "She didn't give him a choice.", "without informing him". This brings up the prospect of picking a time to tell him this summons was on the table.
It seems to me that before her confession, they weren't close enough yet to warrant telling him personal family business;
I think Mirage meant to say that while there was no perfect timing, Lilly could still have picked the least bad timing which a few days after the confession. They had plenty of time alone.and afterward it would be too late (by the standard you're setting). So the only option left would be during. Which I can't quite imagine. "I love you, I love you, don't ever leave me, oh, and by the way, before you accept me, know that I'm thinking of going away forever in a few weeks, so you're playing the odds if you do." Weird. Weird at best. In all, I'm not sure there ever was a good time for Lilly to tell him, given the way their relationship played out.
You're right though that there was no perfect time. Lilly blurted out her feelings during a moment she was an emotional mess, got kind of carried away and after the adrenaline died down, she realized she accidentally set Hisao up for the disappointment of a lifetime, but she wasn't in a position any longer to remedy that. So she kept stalling while secretly hoping for a miracle.