The crime lord was totally devoted to the Shadow Thieves, whom she rightly saw as saving her from retaliation for the actions of her crazed goddess. She was afraid that if she remained in the sea for too long, then Umberlee would seize her.
She did not care about the Cloakmasters of the other three districts of Murann. 
Tren joined the church of Umberlee but left when she discovered she could more wealthy without such a volatile mistress. However, the Bitch Queen cursed her: every day, she had to immerse herself in salt water or suffer an overall decline in physical and mental traits.
Tren found sanctuary when she joined the Shadow Thieves, who protected her from enraged sailors after a vessel—supposedly protected by Umberlee and her priests—sank to the bottom of the sea.