In Her Defence by Philippa Malicka

Wealthy and famous, Anna Finbow stands in court, accusing therapist Jean Guest of brainwashing her daughter Mary to gain access to her trust fund. Jean claims that the dark memories she's helped Mary uncover are real. That therapy has offered her a chance to finally heal from childhood trauma, and she would be better off away from her family's damaging influence. I'll tell you now . . . you shouldn't believe either of them.