Does she worry a lot or its the crowding of thoughts with irritability and anger spells and mood fluctuations as this points towards mood disorder or looking towards the age dementia onset ... lability of mood is seen in bit middle stages of dementia ... but you haven mentioned forgetfulness as a problem so can be safely ruled out ... consult a psychiatrist or neurologist for the proper evaluation

Anger, mood fluctuations, and crowding of thoughts have been mentioned by you as prominent symptoms here, you have also provided that the age of the lady suffering these symptoms is 50 years. Such symptoms at her age can be related to multiple medical, psychological, or psychiatric causes. The prominent ones can be related to menopause, depression, psychological reaction to changing roles, evolving dementia etc. Please take her to a good psychiatrist who can evaluate her condition thoroughly and then only management plan can be worked out. Hope this helps you..