As an archetype, Cancer is very in tune with the emotional state of their interpersonal relationships. Cancer is the mother of the zodiac, and their sensitivity is like that of a mother nursing her baby. An emotional bond is created and both parties become very vulnerable and aware. She is concerned with how her baby needs to be held, stroked, talked to, and looked at to maximize the nurturing experience.
Of course when you apply the archetype to real life, this energy can filter into paranoia or accusation. We can see this energy twisted in situations like Münchausen syndrome by proxy.
My mother is a Cancer for example, and her Moon Aries -> Mars Gemini -> Mercury Cancer (conjunct Sun) Retrograde, causes her nurturing to turn inward. She put her kids through a lot of undeniable neglect and abandonment. If you try to talk to her about it, she nods her head and tunes you out. She has made it clear to all of us that it's her life and raising kids wasn't making her happy, so she had to follow her bliss.
I had a best friend in high school (Cancer Sun, Taurus Moon, Venus Leo), and she would create deep friendships with people. She would also get very upset if her friends had other friends, or began hanging out with each other, or if you broke whatever imaginary rules she used to define the friendship. Regardless of how close she insisted on being though, she would sell you down the river for $50 and a gram of weed.
My ex's boyfriend is a Cancer (I knew him before he started dating my ex) and he is one of the most blatantly mean people I have ever known. He will insult people repeatedly just to see how long it takes them to retaliate. Then he acts offended as if you attacked him out of the blue. If he has a soul, it is the size and color of a poppy seed.
All of these people are so messed up that their nurturing sense has become a self preservation mechanism. I have yet to see a time when any of these three lack an agenda, assumption, or motive based on obsessive emotional misjudgment. My mom senses that everyone wants to leave her, so she nurtures herself by leaving scars that are not easily forgotten. My high school friend senses that others want to take from her, so she nurtures herself by dictating guidelines for the relationship and taking from others before they can take from her. My ex's boyfriend senses that everyone hates him, so he nurtures himself by intentionally being hateful (that way he is choosing to be hated, instead of being hated because there is something fundamentally wrong with him).
So to answer your question in summery LOL: I think Cancer energy is essentially very aware and bound to those they relate with, but can certainly manifest in the ways you describe in unfortunate situations.