Dominant Ne: Mary clicks almost instantly with Sherlock because they are both N dominants. She recognizes instantly that both Sherlock and John aren’t having fun with the wedding planning, and is able to effectively play both of them in order to get them out of the house and having fun. Mary is always pointing out new possibilities for Sherlock, and the two of them seem to enjoy playing mind games with each other. Mary is a bit more of a strategist than most ENTPs, but she’s also able to revise her strategies on the fly. She thinks about her future in every decision, and never does anything that might potentially take her away from that future. She enjoys teasing people and joking about their natures in a friendly, but logical sort of way.
Auxiliary Ti: Mary always takes a rational approach, and can easily set aside her emotions about anything (except losing John). When Sherlock tells her a friend doesn’t like her, she asks calmly who else doesn’t like her. Unlike John, she doesn’t have any difficulty forgiving Sherlock for his short story: not dead. Mary tends to speak and type in logic, but usually in out-of-the-box ways. She’s very analytical and can quickly come to logical conclusions in her head, without needing to talk it out with anyone. Mary is clever enough to figure out where Sherlock would go after he disappears from the hospital. She tends to give short, unspecific answers to questions (whether personal or not) and doesn’t always speak her thoughts (didn’t tell John she hated the mustache).
Tertiary Fe: Mary can pick up on other people’s emotions easily. She recognizes instantly how nervous John is to propose to her (Fe), but is secretly amused by it (NeTi). Mary tends to hide most of her feelings because she’s aware of the future impact that sharing her past could have on her relationships. She has a firm moral code (else she probably would have killed Sherlock instead of wounding him). She knows immediately when someone is being genuinely truthful and willingly helps to smooth over John’s anger towards Sherlock.
Inferior Si: Where Sherlock has to use the Method of Loci to remember things, Mary just pops it off the top of her head like it’s nothing. She instantly recognizes bits of information that she has come across in the past and uses it to help Sherlock. She doesn’t like to think about her past, and spends her life trying to run away from it. She’s also devastated by the prospect of John finding out about it. Tradition is important to her, as is evident in how she handles her marriage.
Most people have typed Mary as either ESTP or ESTJ. However, Mary is extremely intuitive. She instantly connects with Sherlock where other people are put off; when John is proposing to her, it’s obvious that she knows what’s going on etc. Sorry, but she’s not an S type.
For a while I was actually considering ENFP because I thought that perhaps her reluctance to talk about herself was Fi, but eventually I decided that this was actually a logical decision (Ti) that Mary had made based on her future orientation (Ne).
Either way, I’m still questioning this, so my analysis may change a bit if we see a new side of Mary’s personality in the next round of Sherlock.