It seems that she is having extreme anxiety issues which are regarding some fears in her mind and due to avoiding that, she has taken to over cleaning to the point of being obsessive
Next Steps
Please consult a good psychiatrist who can help to ease the problems. Also, work with a psychotherapist who can help her with her underlying problems
Health Tips
Along with medication, she can be guided to keep a stipulated time when she must do her cleaning ritual. Maybe, keep it to 2pm everyday ( and to delay the process of cleaning to a fixed time everyday)