Major Depressive Disorder (MDD): Venus's symptoms of low mood, loss of interest or pleasure in activities, fatigue, sleep disturbances, and concentration difficulties are consistent with a major depressive episode. Her history of depression, including postpartum depression, further supports this diagnosis.

Anxiety Disorder: Venus's anxiety in situations where she feels unprepared and avoidance behaviors suggest an anxiety disorder, possibly Generalized Anxiety Disorder (GAD) or Social Anxiety Disorder.
Adjustment Disorder: The exacerbation of symptoms following her mother's passing and her father's recent death could indicate an adjustment disorder, as these stressors may have contributed to her current symptoms.
Attention-Deficit/Hyperactivity Disorder (ADHD): Venus's long-standing difficulties with concentration, memory, and completing tasks could be indicative of ADHD, although this would require further evaluation.

Dementia or Neurocognitive Disorder: Although less likely given Venus's age and presentation, it is essential to rule out a neurocognitive disorder, as the symptoms of memory and concentration difficulties could be indicative of an underlying neurodegenerative process.
Sleep Disorder: Venus's struggles with falling and staying asleep could be a primary sleep disorder, such as Insomnia Disorder, which needs to be addressed as it can exacerbate other symptoms.
Substance-Induced Disorder: Although not mentioned, substance use could contribute to or exacerbate Venus's symptoms, making it crucial to inquire about substance use.

Traumatic Brain Injury (TBI) or Other Neurological Conditions: A TBI or other neurological conditions could potentially explain Venus's cognitive symptoms, although there is no clear history provided that would suggest this.
Endocrine Disorders: Certain endocrine disorders, such as hypothyroidism, can cause cognitive symptoms, fatigue, and mood changes, making them a consideration in the differential diagnosis, albeit less likely without specific indicators.