I struggle with this style game (escape room, deduction) but was engaged enough to push through and get to the end.
I think you've got a great difficulty mixed throughout. I think the repeat puzzles (the storage each sister was using) was brilliant - repeating the sense of accomplishment and being rewarded with more story.
And they story has a wonderful balance of details and vagueness. I have such a clear image of what happened and at the same time, so many questions and I'm sure every person who finishes has their own idea as to what all happened.
I can't compliment the design an implementation enough. I hope you get to keep doing this for a long time.