Its a personal thing really. Shes a very chaotic woman.
For example, just before the scene in question she tells the MCs wife thats shes going to fuck her husband... to her face.
Not sure if it was just to spite her or not. Maybe its just that Kalestra does whatever she wants and has no respect for anyone else.
Either way I dont like it and I dont like not getting a choice about the lewd, hence my disgruntled attitude.