Hahaha, this. But seriously now, for some reason, I really think Aizen has something to do with her death.
did ichigo kill her ? Hmmm not sure that would be devasting reveal to ichigo he might just kill himself .... I think it's vandereich , Masaki was a kurosaki one of the strongest Quincy families .... Maybe they went to search for her cuz he needed to make new pure blooded babies ( just an example) but when he saw that her soul was infected by a hollow he might have
1) killed her
2) try and find a way to cure her ( she might not be dead)