Psychology is a science (even if in its origin it was itself philosophical, or born out of philosophical discourse and reflection). As such, it aims to ground the understanding of the human mind and behaviour in methods that yield measurable results.
Despite controversies even amongst psychologists/therapists, their treatment hinges on a therapeutic paradigm that rests on a clear understanding of health and unhealth. On the basis of this understanding, unhealthy mental and behavioral patterns are detected, classified, and causally determined with diagnostic, prognostic and treatments to boot. Sessions then aim to first diagnose a patient (methods may vary), elucidate causes (either exclusively by the therapists or in conjunction with the patient), and then proceed to implementing treatment.
Sessions conducted by philosophers do not follow this pattern at all. Philosophical counselling draws clients into an intra-personal and inter-personal dialogue that aims to elevate counselees from a static, or stagnant state of thinking and behaving to a self-reflective state invested in a deeper, more synthetic and analytic understanding of self and the world.