The way Maria answers to journalist tends to show that she's not very fond of them, which shows she's wise, journalists are capable of doing crap to anybody in order to sell newspapers, so those reports that Maria is moody with journalists is probably true.
Towards players, I think the same applies. They are not supposed to be her friends, they are supposed to be the ones she's gonna beat at any cost. I think Maria is very proud of her achievements which is totally legitimate. Then probably, she's not going to make the first step towards the average player, she considers that the average player is the one who would show respect to her. I don't think that if any girl passes in front of her and then says hello, she would ignore that person.
IMHO, Maria is a very self-centered person (I generally recognize that kind of personality for being one, lol). She has reached a status that makes her being on her guard about almost everyone. She considers any person as potentially harmful, and that's not so wrong.
Last thing, my perception is that Maria doesn't appreciate that much to be a celebrity. She knows she has a role to play for her agent IMG, for the WTA, she accepts to do it but she's not eager to it. Maria's will is about winning and having a comfortable life. Not really to be in the spotlight.
OK, everything I say is pure speculation, but I consider myself to have some psychology and when I analyze the way Maria acts and what she says, that lead me to these conclusions. Nethertheless Maria is probably a person who's greatly worth knowing personally and having a real-friendship, but it certainly takes from you to be someone exceptionnal, just like she is.