They fast-tracked the trust between Carrie and Dante to an absolutely absurd extent. She is trusting him with her operation, her illness (and wellness), her fears regarding her daughter, and her conspiracy(?) theories. He is 1000% playing the role for Carrie that Quinn would have under these circumstances.
If and/or when it is explicitly stated that Dante is a bad guy, it is going to crush her. It will be like losing him all over again, in a way, because she’s going to be forced to confront what a rare friend she had in Quinn.
This is not to suggest that she viewed Quinn as replaceable, by the way. It’s more that she is really, really, really lost without him, and she’s just desperate enough to allow herself to believe that Dante can be what she needs.