I really doubt if they will get Kajiura just for arranging music lol. And she was credited only for Theme Song. Hope they won't pull another Kimetsu here like what is happening right now they thought Kajiura will be the composer lol. The best thing would be: insert game songs to the film(else we will get another war lol) and add variations of the theme song+ending theme song(Japanese ver.) from FICTIONJUNCTION KEIKOHm so maybe she was just tasked with the arrangement and lyrics of the bgm, not composition. Its still really lovely :))
Looks like odds jobs to me lol: 1 song here, one arrangement there, nothing project-like so far apart from the known stuff. Event though this does help to make her name known.