The correct option is B debility
Option B: 'Debility' means 'a weakened state'.
Option A: 'Incubus' is 'an imaginary demon or evil spirit that descends upon sleeping people'. It's an imaginary idea.
Option C: 'Obsession' means 'a domination of one's thoughts with one particular idea'.
Option D: 'Delusion' means 'a false opinion or belief'.
Option E: 'Hypochondria' means 'excessive worry or talk about one's health'.
From these options, 'debility' is most appropriate, and completes the sentence in meaning: she had a terrible night because of her weakened state.
Hence option B is correct.
The other words are not relevant to the given sentence. They cannot take place during one's sleep. Hence options A, C, D and E are wrong.