So... and this is before the translation of the following pages... the mistress/Milady is dying from [anime fatal disease #12], and the had the android version built for either a brain upload, or just to be programmed with her mannerisms/data as a replacement. The sister is only aware that the (present day) Milady isn't the original human body, and thinks that regardless of what was done it isn't really her sister and thus an insult to the original's memory, hence the assassination attempt(s).