So the final paper for a course I am in has me read a case and give a diagnosis, assessment, etc. Here's the case I picked:

Case 2: Sara

Sara is a 23 year old Caucasian female presenting with increased suicidal ideation, as well as a recent suicidal attempt of an overdose. She is complains of increased feelings of anger and irritability and has expressed feelings of hopelessness and worthlessness. Sara has had several hospitalizations with the most recent occurring after a recent trauma which occurred at a party off-campus, where she had been drinking and was assaulted. She reports getting little to no sleep because of increased nightmares and dissociative flashbacks. Recently, her parents have been experiencing marital struggles and are currently in the process of separating. Sara and her younger sister, 16, have a strained relationship with little support from their parents. Sara cries, “I just feel so out of control and lost!”

Substance Abuse: no history

Medical: no history

Psych: first visit

Now I'm stuck between two diagnoses and here's my rationale for each:

MDD: Suicide attempt, suicidal ideation, feelings of hopelessness and worthlessness, feeling out of control

PTSD: Recent trauma (SA), flashbacks, nightmares, insomnia

So, I’d like to diagnose her with MDD, as I think that could led to either insomnia or hypersomnia, however she presents with insomnia. Then, would I mention a differential diagnosis of PTSD due to the recent trauma and the flashbacks/nightmares because of it? I want to make sure I am on the right track before I start drafting the paper.