I don't think Enid had to be spiritual to be a great writer. Everyone can create atmospheres if only they would take the time to reflect, observe, think, and write it out. I don't think the sixth sense thing is anything special. Everybody intuitively understands some things others don't, and in the case of relationships (familial, platonic, romantic, etc etc) these intuitions are heightened.
Similarly different situations bring out different reactions in people. Stress triggers adrenaline, the fight or flight hormone - some in a situation such as entering the Hidden House, would want to walk away ("flight") because they had a "feeling" of foreboding, while others would want to stay back, explore, and take chances ("fight") because they have a "feeling" of excitement. I am sure there are many other such hormones that regulate these actions (cholinergic substances and decision making, etc.) and it has very little to do with spirituality.
