Considering her repeated declarations in game that she trusts only two people, being Vergil and Red Hood, I would not consider her to be receptive to trusting others. Based entirely off of game interaction, it appeared that she and Vergil had some sort of history, while it's turning out that there really was none.

Rushed seems an appropriate term when a situation goes from enemies that barely know each other to attraction and complete loyalty/trust within a month, particularly considering her occupation and his species.