Both are glamorous women. Both fashionable. Both smart and savvy about their public personas. Both equally powerful and influential when it comes to the President of the United States.

But despite maintaining a warm relationship over the last two decades, stepmother and stepdaughter have found the White House years more challenging, according to a source familiar with the dynamic who notes friction between the two.

Of late, the two women are described as "cordial, but not close," by someone familiar with both. Months of overlapping objectives, trips, events and interactions with the President have created a shaky alliance, as reported in "Free, Melania: The Unauthorized Biography," available Tuesday.

A spokeswoman for Melania Trump, Stephanie Grisham, tells CNN that the two women "always shared a close relationship and still do today."

Melania Trump's first big solo trip was to the African continent , as was Ivanka Trump's first big solo trip. The first lady was the first to introduce highly produced mini-videos of her events for public consumption, and now Ivanka Trump also makes her own short films, with voice-overs and music. While these points may seem trivial, the similarities have reportedly caused static.

On presidential trips, when Melania Trump goes, the first daughter's profile diminishes -- and when the first lady is absent, Ivanka Trump steps up.

It has created an odd dynamic that has left Ivanka and Melania Trump switching off front seat-back seat as the two women in Trump's orbit, a relationship that has created friction.

It was during Trump's presidential campaign that family life shifted to politics, and the dynamics changed as well.

Melania Trump, uninterested in the constant travel involved on the campaign trail, and hoping to maintain a semblance of normalcy for her young son, stayed away for the most part, remaining in New York City. Out on the campaign trail, it was Ivanka Trump who stepped into her space. Ivanka Trump, a seasoned public speaker who is comfortable in the spotlight, was able to serve as surrogate campaigner in lieu of Melania Trump.

The President's daughter maintained her role as one of the most prominent female faces of the family and administration, moving immediately to Washington, setting up her office as a senior adviser to her father. Her portfolio also grew to include more championing of issues around women and family, which have traditionally been the domain of first ladies. Ivanka Trump lent her support to women's economic development, child tax credits and pushing for STEM programs for children and young adults.

"The most important investment we can make as a country is in the next generation of Americans, and we're doing just that through our tax code," said Ivanka Trump in one of her social media videos, designed to capitalize on her photogenic popularity.

Ivanka Trump also learned to navigate the media, often selectively leaking her involvement, or lack thereof, in headline-making policies.

The tension between the two manifested itself over credit for influencing the President into changing his mind on one of his administration's most controversial policies: child separation at the border.

When images of children being separated from their families flooded Twitter feeds and news programs last year, a source said Melania Trump told the President the zero-tolerance policy had to end, and quickly. She organized a trip with little notice to fly to McAllen, Texas, and see for herself what was happening at an immigrant intake facility.

"I'm headed down to Texas," Melania Trump told Donald Trump, according to one White House source.

Shortly thereafter she went, but she didn't leave until she was certain her husband would sign an executive order ostensibly ending the zero-tolerance separation policy.

Ivanka Trump, at the same time, was also letting it be known that she was trying to convince her father to pull the plug on zero tolerance. This all coincided with a few punishing days for her on social media. (As the photos and stories of families being torn apart ran rampant, Ivanka Trump had posted some personal shots of herself and her young sons on Twitter and Instagram, a move that her most gentle critics called "tone deaf," and the harsher ones deemed an example of her living "in a bubble.")

Both women, separately, and with their own signature styles -- Melania Trump quietly and one-on-one with her husband, and Ivanka Trump via the media and her relationships with lawmakers -- were pressing for action.

When the President did sign the executive order, he gave both women credit.

"Ivanka feels very strongly about it," but also, next breath, "My wife feels very strongly about it."

But Melania Trump boarded her government jet wearing the now-infamous, $39 "I really don't care, do u?" jacket , a lost-in-translation message that was possibly a jab at Ivanka Trump, for drifting into the first lady's lane.

Melania Trump wearing anything that inexpensive, much less from fast-fashion brand Zara (a label worn with frequency by Ivanka Trump during that period,) was out of step with the first lady's regular sartorial preferences, and overt negative messaging was not by experience or observation Melania Trump's style. Her spokeswoman, Grisham, after the offensive jacket took over the news cycle, officially said that she had worn it as a message to a meddling media.

In a way, Ivanka Trump and Melania Trump are splitting -- and will continue to split -- the traditional roles that most spouses or female counterparts to male politicians have, but they share the most critical component: the President's ear. They are the only two members of the administration who have the freedom and power of total job security -- one a first daughter and the other a first lady.