If you notice someone has narcissistic traits, or she seems a little too eager to ferret out details of your life, be very careful of what you share. Most importantly, do not disclose sensitive information. In addition, you need to keep all other aspects of your whereabouts closely under wraps, even if they are not particularly "sensitive."
That's because malignant narcissists take innocent facts, attribute the worst possible motives, blow them out of proportion, and then invent stories to ruin your reputation. Say, for instance, you are happily married, but, last weekend, you traveled to visit your sister, who lives out of state. Your husband didn't come along on this trip because he had a lot of work to do. But he didn't mind if you went, because he knows you and your sister wanted to spend some time together.
If a malicious person catches wind of this innocent trip, she could assume that something is wrong with your marriage. (Probably because hers is on very shaky ground.) She'll start asking more questions, such as how often you visit your sister, without your husband. If she's targeting you, or plans to, she'll file this information away, along with the rest of the details she's now gathering.
For a time, she'll pretend to be your friend. Meanwhile, behind your back, she'll paint you as unstable because your marriage is "falling apart." She'll use the trips to your sister's house as "proof," along with her additional embellishments. People will believe her because malignant narcissists possess the gift of persuasion.
Plus, they build their case upon real facts, such as the weekend trip to your sister's. Because other people know this to be true, since you've shared it with them as well, they'll assume everything else they hear about you is true as well. Someone with a serious moral disorder may even invent a wild story of how you are also cheating on your husband. And since they have that little bit of real information, which you happened to mention, they can do a lot of damage.
This is all part of the narcissistic grooming process, where they are sizing you up before they attack. Even innocent, everyday events are used against you. So, when a narcissist is in the picture, don't share anything. Everything you say can and will be used against you.
Be especially wary of disclosing any personal information in the workplace. Nowadays, it seems as if every office with more than a few workers has a bully in the mix.