And there was no way for Lisanna to know that her siblings hadn't gotten over her death. (whether they've "gotten over it" is debatable) - all she knows is that the ones she knows right now will be said if she does anything. Furthermore, until the reverse Anima was activated - there was no known way back. Even Mystogan had no idea.

I guess the part that made me cringe the most in DE's post is that he described Edo-Elfman and sis as "fake".