My father passed away in January, my 6y.o and he were exceptionally close, he was her dad too.

Over the pass few months, she has cried maybe 3 TIMES, and communicated her anger (calmly) over his abrupt passing. ( Stroke + Heart Failure)
She has made it VERRY clear that she will not be openly sad or discuss her feelings about his passing b/c she does not want to upset me or my mother. She flat out refuses

I didn't know what to make of her decision, but recently she's been having trouble sleeping, I think her buried feeling just got exhumed, and it's manifesting in her sleep.

She screams and cries for him every night, despite the sleep aid the Dr provided, needless to say she wakes up exhausted and does NOT look forward to school...
She used to be very sweet and laid back, now she's snappish, irritable and cries at the drop of a hat.

My hands are tied as she won't open up to me, I feel inadequate...

IS it possible that she is suffering from PTSD 8 MONTHS LATER? and at the age of 6?? More importantly, whatever the label... HOW DO I HELP HER?

Looking forward to your input