She’d tried to put distance between herself and the bloody life that was part and parcel of being a member of the Segreto. Lena didn’t want to be a part of that brutal existence, of endlessly tracking evil down and destroying it. Even if one didn’t get killed, the legal ramifications of being caught destroying demonkind were huge. Alex’s ability to sense those of demon blood was rare in full humans. The typical person had no clue such beings were in their midst, and law enforcement would see the Segreto’s holy war as murder of innocents.
Not to mention demonkind fought back and were just as happy to kill the Segreto off in grisly ways.