She had warned him on the very first day met that she wasn’t a very good person. He doubted her and said “Don’t worry, it’ll be alright.” She accepted his nonchalant response because, well, she had warned him, and she wasn’t a very good person. Also, He would be very useful to her own interests in the long run.
So, when she back-stabbed, took bribes, and sold him up the river as soon as it as convenient for her, she didn’t even bat an eye. After all, she had warned him, and it wasn’t her fault he didn’t listen.