Sheila used to ring her father a lot during the early hours,for someone to talk to,so his sleep must have been disturbed on many an occasion.
I don't doubt that during the short-lived stay at WHF prior to the tragedies that Sheila thought that things were the same as ever between her and her father until she'd learnt that her mother was visiting her GP regularly for whatever reason,though Nevill thought it was a good enough reason to shower his wife with the sympathy for once and help he'd once willingly given to his daughter,which obviously Sheila hadn't readily agreed with.
One time when Sheila was staying at WHF during a convalescing period June had remarked to Sheila as not having been the only one who was unwell. In other words,little sympathy came from her mother so on the night of the 7th Sheila repaid them all back by shooting them all dead.
What, exactly does "a lot" mean, Lookout? Do we KNOW how many times she called her father? Given that it was a family which held secrets, I can't see them sharing with Sheila, ANYTHING which might give her extra cause for concern.
Most people who suffer with depression are hugely self oriented. I've no doubt that Sheila was the same. It may have been, one one occasion, that June, who I imagine to have been a bit of a martyr, was fed up with Sheila's me,me,me stance, especially if she hadn't noticed that June was unwell.