Quite possible! I estimate that the level of "strange" behaviour will be depending on how we guide Willi. Ocean mentioned a NTR path for Leia, which I think will come into play mostly if the MC tries to keep a larger distance to Leia or worse in Leia´s sight, turning towards Kati.Agreed. But it'll take time before she learns all that I reckon, so I'm expecting a lot of irrational behaviour from Leia. Then it's up to the player's action to guide Willi. Back to Miru, into one of the other LI's or will you break Leia's heart and soul and end up with Katie...
I do not think we will see all that much strange behaviour from Leia if we from the start keep close to her, no matter if we are true to Miru or in an open relationship. If the story form old WIAB, where Willi was framed for a crime he did not commit, is at least partially still in the game, I think despite her jealousy Leia will warm to Miru for being there for Willi and get totally pissed at the people who did this to him.
Btw, what are your top 3 LIs in WIAB? Mine are Miru, Leia and Dana/Daphne sharing their position.