Genuinely baffled by her sister's thought process here.
dysfunctional fucking family but im not a werewolf so maybe its just their disposition.
The issue isn't her sister's thought process, the issue is the mangaka didn't think things through at all.
How the hell is training to resist desire for blood supposed to work if you're not exposing her to blood to get used to it and learn to control herself? It seems they didn't once test it in
all that time? Zero thought went into this manga.
That's also why her sister's action don't make sense, mangaka didn't bother to think through the consequences, probably because from his point of view it was obvious nothing was going to happen so why bother to think of what could go wrong?