This is the most common question and misconception people have in regards to coaching. Coaches should never try to replace mental health care in any way. Some psychologists and similar professionals also end up becoming coaches to be able to help their clients in different ways.
Coaching is much more about a co-creative partnership and accountability than fixing or healing. It requires a state of mind that allows for working on goals in a proactive way. A client can work with a coach also while in therapy, if the therapist agrees it’s a good idea.