Get her detailed evaluation. As your presentation suggests symptoms of OCD/ depression. Do consult a psychiatrist/ clinical psychologist for the needful

Your statement of problem is inadequate.

Hi, it looks like she is stressed about something. To feel better she will require Counseling and she will need to consult a psychologist. It is known that depression, anxiety, or stress can cause forgetfulness. She can consult a doctor as well to check if physical symptoms is causing forgetfulness. Do not worry too much consult a doctor and psychologist.

I think, her old past unpleasant memories are disturbing her.. It is better for her to talk to a professional person, so that she could vent out completely all her ill feelings.. Fix an appointment with a therapist on behalf of her.. That would be the most important thing ever you people all could give her.

When a person is not well physically it has an impact on your mental health but it needs to be checked what the physical symptoms are to which anxiety symptoms follow.It might be like she is taking too much of stress and is not able to attend and register things in her mind and hence forgetting things.Needs to be checked if these symptoms which you mentioned surface only when she is Physically unwell and for rest of the days she is fine,if her coping is intact when she is healthy why she gives in when she is unwell.