Re: Libel Question
If the sketches, etc, are intended to be private there is no public libel. People write, journal, sketch unflattering things about others in private diaries all the time. I have never heard about such a case leading to legal action.
Should the subject of the sketches find them and feel sufficiently threatened to call the authorities, the authorities will question the artist. If the artist responds that the work is part of a private journal working through past issues and clearly demonstrates that there is no present threat, that should be he end of that.
Art and journaling about past traumas is an accepted and appropriate therapeutic modality in many cases.
In this situation I think the biggest risk of harm might be if the subject saw the works and was upset enough by them to take action (physical, mental, emotional,nor legal) against the artist.
If and when the finished works are published, the "Everyman" test might be applied to determine libel. That is to say, would an ordinary person viewing the works identify the person being depicted as a specific individual. If the subject and those close to him/her was able to detect the pointed reference, but a person unfamiliar with the intimate details of the subject's life would not make the connection between subject and painting the artist is probably safe from libel.