

MACHINE-TRANSLATED snippets from spoon.2di magazine #138, interview with Koide and Kawahara regarding the finale.
Image 1: Koide, Image 2: Kawahara
Please note: this is a MACHINE TRANSLATION of Chinese text, which was itself translated from the original Japanese magazine. Thus there's things like Mari -> 'Mori' and Lara -> 'Lala'. So please take these translations with a pinch of salt!
If we're to take this at face value though, this pretty much matches what I had in mind regarding the ending - even if Lara leaves Shiga, her and Mari are still connected via their true love in their hearts and their relationship will continue. Thus, Mari is able to smile despite Lara's departure, knowing she isn't truly alone.