Does this mean "she clearly remembers her departure" or "she remembers her departure clearly"? It seems to accept both but they don't mean the same thing...
Why can't it be "his departure"?
Because "sin" indicates it's the subject's departure, not someone else's. So it can only be "her departure" in this sentence.
So, how would the translation than be of ' she remembers his departure' ? Hun husker hans afrejse?
And if she remembers another female person's departure, it would be "hendes afrejse".
Why is it Tydeligt and not Tydelig?
It's an adverb. See the tips https://www.duolingo.com/skill/da/Adverbs
Kan sætningen også betyde "She obviously remembers..."?
She is in the afterlife among the angels, and clearly remembers the moment of her death (departure).
"she clearly remembers" is a split infinitive and frowned upon.