So we all know that Chloe makes Lucifer vulnerable. He doesn't loses his powers just his immortality. Which to a angel it's a big deal.
But why do you think that happens?
She clearly didn't caused that to happen when she and Lucifer met. It was only as their partnership began to grow that it started to happen. Also when they met she was (and still is ) totally immune to Lucifer compulsion.
So what are your theories? Do you think she's a nephilim or a descendent from one? Is she perhaps something else, something she doesn't know she is? Or is she somekind of test god placed in Lucifer path? Maybe a way for Lucifer to finally understand what it means to be human and for him to understand all the things he finds so irritating or boring about humans?