Both children relied on their parents and they were not independent.
Out of both children though Shelia was the one who had much greater problems ( only surface talk though because if Jeremy is indeed gulity of what he is in prison for he had greater " mental problems than shelia ) he just hid it behind a cloak of " outward respectablity"
Going back to Shelia though the fact she managed to look for work and tried to keep a semblance of normality " social occasions, work, travel etc whilst battling with what she was battling with can only be commended as far as I am concerned. For all her problems she still showed some nous.
Unfortunately, there is no known treatment for entitlement, just like there is no treatment for Narcissism or Psychopathy. They are mindsets, all of which can remain hidden "behind a cloak of outward respectability".
Was Sheila actively seeking employment at the time of her death? I'm thinking she'd hardly have had time. Just out of hospital, she spent time with Christine -there seems not to have been any problems with her meds then?- after which problems arose which would have taken time to resolve. So now, the time is getting near to the visit to WHF prior to the twin's holiday to Colin's sister in Denmark. It was during this that friends report her as being lethargic, unwashed and unkempt. None of which paints a picture of a woman seeking employment, does it?