Maria hadn't had a boyfriend in three years. Too much of a hassle.
That is not the way to do it, m'friends. It makes the character sound bitter.
Now, if the character is bitter, this works. But the thing is, if you are trying to make a female character who literally can stand on her own two feet as a person, you fail. By basing her personhood on the fact that she doesn't need a man, you have just made her characterization all about the man that she "doesn't need".
It depends on the character that you are trying to portray, but too often, this is used with the intent of creating a "strong female character". Then, nine times out of ten, this character then runs into a man who then does everything for her. But we are supposed to believe that this female character is strong, because we were told she doesn't need a man.
Instead, the way to handle a female character who "doesn't need a man" is just to have her functioning without a man. No need to draw attention to it. Just have it happen.
Needing or not needing a man to "complete" a character are not necessarily good or bad things. It all depends on how they are handled.The influence of a male character on the female character doesn't necessarily mean she is "weak" or "underdeveloped" and likewise, a lack of male influence on a female character doesn't necessarily mean she is "strong" or "independent".
Basically, it all comes down to treating the characters, both male and female, as people.