The phrase "a close friend of hers" is correct and usable in written English.
You can use it when referring to someone who has a strong friendship with a female individual.
Example: "She often confides in a close friend of hers about her personal struggles."
Alternatives: "a dear friend of hers" or "a good friend of hers."
In 2007, just before she died, Ms. Cohen changed her will to make Mr. Perelman, rather than a close friend of hers, executor of her estate.
I'm not a close friend of hers, I'm not intimate with her in person in any way, but it's just simply true and we see it when you put her one-on-one with people and in small groups of people or, for that matter, large groups of people where there is nothing between her and the populace, the voters and/or the press — she's very effective.
Amanda Cynkin, a close friend of hers, said that Ms. Stokowski had confided to her shortly before that she had dreamed of meeting a man who was "passionate, interested and interesting: basically, Anthony".
Three years ago, the group killed a close friend of hers, a man who was like a father to her.
Price spoke about her role in the disappearances and, in particular, about her grief over the death of Joe Lynskey, a close friend of hers.
"There's a cult of Margaret Kilgallen, Dan Flanagann, a close friend of hers from the library, says.
"When Leah came back from the wedding, whatever happened happened... Leah had brought up to a very, very close friend of hers -- at our house, in private -- you know, 'I just think it's really weird how involved Tom is with the upper levels of the church.' She just started kind of questioning a little bit what was going on and just... how involved he was with the upper level people.
"The idea had many parents, but the execution was hers," Roger McNamee, a venture capitalist and investor in Facebook and Google, who is a close friend of Sandberg's, says.
