Offering to cooperate with other people if they cooperate with you:  It's simple.  It works.  It's the core of Civilization.  You hear it before you're old enough to understand the words.  There will not be a bloodbath, and she will find a way to allow Isabella to know what she knows.

"I also need to learn enough about your world to see if there's any knowledge I can apply to become wealthy - for example, if you have psions who can discern truth, it seems like you could have mate-matchmakers even more trustworthy than ours, perhaps you simply haven't had the idea.  I am also dath ilan, in this place I am all of dath ilan, and I will also help if I can."

Offering to cooperate with other people if they cooperate with you:  It's simple.  It works.  It's the core of Civilization.  You hear it before you're old enough to understand the words.  There will not be a bloodbath, and she will find a way to allow Isabella to know what she knows.

"I also need to learn enough about your world to see if there's any knowledge I can apply to become wealthy - for example, if you have psions who can discern truth, it seems like you could have mate-matchmakers whose oaths are even more trustworthy than ours, perhaps you simply haven't had the idea.  I am also dath ilan, in this place I am all of dath ilan, and I will also help if I can."