It's alright.

[ Or at least, it's alright enough that she feels like she can explain what happened without becoming a mess. It wouldn't do to keep being sad about Thoma's absence; he was a bright spot in both her and Diluc's lives, and he surely would hate to see their happiness eclipsed by his departure. She and Diluc have promised to keep on despite it all... ]

Aha, you're probably wondering how it happened, right? I know it's a bit unconventional, but... I guess the simplest way to say it is that we all fell in love at the same time. Thoma was the one who suggested we all be together, actually. To be honest, if not for that I'm sure I would have taken myself out of the picture...

[ There's a lot more to be said, about how at the time she hadn't felt deserving of love, about how she's the only one of them who doesn't come from Teyvat, about how if they were to leave this place she would be the only one separated by worlds. All worries that Thoma would continually ease, now brought once more to the forefront now that he's gone. ]

Anyway, now you know! I'm sorry I didn't say anything until now.