I have had many times when I had a bad feeling about a person who I had no choice but to be around, either because we lived close or worked together, so I watched, making sure NOT too let them get close enough to do any damage should I be right. This is how I went from NOT trusting my instincts to validating them.
I tend to put people in a box based on my instincts, that way I keep myself from being harmed but I don't cut myself off from everyone.
For instance, I trust my neighbor implicitly, with my home, with my daughter anything really. We have known each other for 5 years, since I moved here. There are people who I have known longer, people with whom I have more history, more in common with etc. that I don't trust near as much as I do Marlena. When I first met her I had a good feeling about her, she extended a helping hand to me at a time when I needed it without becoming too intrusive, over time of watching her I saw I could trust her. My feeling was right.
I also used to have a friend at work, she was a wonderful girl but communication was not her strong suit. Her husband was a pot smoker to the point where he allowed his habit to threaten his ability to take care of his family. In the field in which he works, most places require drug testing, I watched as he left the majority of the work on his wife's shoulders because of this AND I watched as she allowed it too happen without saying a word to him. She was paying the bills, the primary bread winner, the primary caregiver for their child, he would not do a thing with the child, instead dropping the child off at his Mothers home, AND she went too school while doing all this, all the while being a doormat for her husband. My first instinct, when I first sat and talked with her when we were training was that while she was a nice person, she was a doormat and someone I could not fully trust because of this. In the end I was proven right. It was imposible to have a relationship with this person unless you wanted to live as a doormat to her husband like she evidently wanted to. Not my bag, thanks...