Seven months later, Ms. Trump is her father’s all-around West Wing confidante, an adviser whose portfolio appears to have few parameters, making her among the highest-ranking women in a senior staff stocked almost entirely with men.

The two trade thoughts from morning until late at night, according to aides. Even though she has no government or policy experience, she plans to review some executive orders before they are signed, according to White House officials. She calls cabinet officials on issues she is interested in, recently asking the United Nations ambassador, Nikki R. Haley, about getting humanitarian aid into Syria. She set up a weekly meeting with Steven Mnuchin, the Treasury secretary…

During the campaign, Ms. Trump successfully pushed her father to praise Planned Parenthood from a Republican debate stage, a moment that created a stir at the time because of the party’s broad opposition to the organization’s abortion services. But more recently, with congressional Republicans threatening to cut all funding to Planned Parenthood (even though the women’s health organization says it receives no federal funding for abortions), Ms. Trump approached its president, Cecile Richards, to start a broader dialogue. She also had a proposal: Planned Parenthood should split in two, Ms. Trump suggested, with a smaller arm to provide abortions and a larger one devoted to women’s health services.

White House officials said Ms. Trump was trying to find a common-sense solution amid the roar of abortion politics. But Planned Parenthood officials said they thought Ms. Trump’s advice was naïve, failing to understand how central reproductive choice was to the group’s mission. Ms. Richards sharply criticized Ms. Trump for not publicly objecting to the Republican health care bill that failed in March, and Ms. Trump felt stung.