WASHINGTON — Nearly a year into her tenure as first lady — and after a week of intense scrutiny prompted by a new book that claims she had dreaded life in the White House — Melania Trump has hired a director of policy to advance her nascent platform.

For months, Mrs. Trump’s East Wing had searched for a policy director who could further an agenda that has been broadly defined as helping children. On Thursday, the White House announced the first lady’s choice: Reagan Thompson, 27, who had previously served as an executive assistant on the National Security Council.

Before working for the N.S.C., Ms. Thompson was a communications and policy adviser for Mike Pompeo, the C.I.A. director, when he was a hard-line Republican congressman.

It is unclear how Ms. Thompson’s background in serving Mr. Pompeo — she has described her duties with him as “working on issues for the intelligence and Benghazi committees and on Iran, Guantánamo and Asia” — may help her in her new role.