Could you please tell me the litteral and metaphorical meaning of "indiscreet" in this excerpt of chapter 7 of The Great Gatsby by F. Scott Fitzgerald? Does-it mean that her voice "can't keep secrets", "betrays her", or that it is "imprudent", "inconsiderate"?
“She’s got an indiscreet voice,” I remarked. “It’s full of——”
“Her voice is full of money,” he said suddenly.
That was it. I’d never understood before. It was full of money—that was the inexhaustible charm that rose and fell in it, the jingle of it, the cymbals’ song of it.... High in a white palace the king’s daughter, the golden girl....
Your interpretation is correct. The term here is meant to suggest that Daisy's voice is full of an emotion that will give her situation away (regarding her feelings for Gatsby). On the most literal level the term "indiscreet" refers to a lack of tact and/or good judgement.
Looking at the context of the line: This line appears during an episode where Gatsby, Tom and Daisy are all together at the Buchanan house before they set out for a trip to the city. Before Nick says that Daisy's voice is indiscreet, she has already kissed Gatsby on the mouth when Tom left the room.
Gatsby tells Nick that he can't say anything to Tom in his own house, implying that he would like to challenge Tom and have things out about Daisy but feels that the time is not right.
It is here that Nick says, "She's got an indiscreet voice." The suggestion seems to be that Gatsby may not have to say anything to Tom because Daisy's voice may give away the secret on its own.
There is also a subtle suggestion from here that Daisy is going too far, being too bold, and that she, perhaps, close to being obscene in her boldness. This is the more metaphorical connotation of the term "indiscreet" as it is used by Nick.
Gatsby demonstrates his firm fixation on Daisy in his response, while also showing an unexpected clarity of view regarding her character. Gatsby idealizes Daisy but also sees her for who she is.
In this observation the tag Fitzgerald repeatedly uses in his identification of Daisy—her low voice—unites with the motivating force in her life, money, seemingly a motivation Gatsby has quietly understood and accepted.