What was Palm Beach socialite linked to Donald Trump Jr. doing sitting behind him and fiancée at RNC?

She’s the lady in red!

Page Six has learned that socialite Bettina Anderson was sitting directly behind Donald Trump Jr. and his fiancée Kimberly Guilfoyle at the recent Republican National Convention.

The Daily Mail reported last week that Don Jr. was seen looking cozy with Anderson — and even “locking lips” — over brunch recently at Honor Bar in Palm Beach, and that it’s the “talk of the town.”

The tabloid published further pics of Anderson and Don Jr. attending the same party in Jupiter, Fla., last month, which was allegedly not attended by Guilfoyle.

Anderson, 37, can also be seen in photos, Page Six has learned, sitting behind Trump and Guilfoyle at the convention in Milwaukee, Wis., in mid-July.

The fashionable socialite attended the Wednesday night of the GOP event, and can be seen in pics applauding in a glamorous red outfit.

She was also photographed chatting with Don Jr.’s ex, Vanessa Trump, 46, at the event, and we hear the two are close friends. Sources said she attended with Vanessa.

In some shots, the duo were seated next to each other, and are also nearby the rest of the Trump family.

Anderson also can be seen in background of an image posted by Don Jr. on Instagram of himself and Hulk Hogan at the convention.

A GOP insider told us that the seat where Anderson was spotted was “open” and “not an assigned seat.”

Back in Palm Beach, depending on who you talk to, Don Jr. and his fiancée of four years Kimberly Guilfoyle are on the rocks — or going stronger than ever — at the same time the couple is headed to appear Friday at a Texas conservative youth conference.

Trump allies say the brunch photos with Anderson were overblown, and just part of a campaign to slime Don Jr., 46.

Both sides also point out that Anderson is a close friend of Don Jr.’s ex, Vanessa.

“Don and Kimberly haven’t been getting along over the past year,” a source tells Page Six. “They get argumentative at Mar-a-Lago in front of people. Nothing crazy, but you know when a couple is fighting. They bicker in public.” 

But a series of Trump insiders insisted to Page Six on Thursday that all is well between Trump and Guilfoyle.

“They are 100 percent together. They love each other,” said a source. Another friend of the Trump family also tells us the pair are “as close as ever.”

We hear the couple is still living together, will continue to campaign together and will also head on a trip to Europe.

After the Daily Mail’s report, Guilfoyle posted pics showing the couple at an event called Patriot’s Day Freedom Fest where she was planting a kiss on his cheek.

Anderson, for her part, posted an image to her Instagram feed that said, “Gossip is the devil’s telephone. Best to just hang up. -Moira Rose,” (cheekily referencing an over-the-top character from the show, “Schitt’s Creek”).

She posed in front of a sign that said, “Private,” for good measure.

She later posted a clip from “Meet Joe Black” in which Anthony Hopkins opines, “Love is passion. Obsession . . . Find someone you can love like crazy.”

The socialite has also previously posted the a moody black-and-white shot with the caption, “She didn’t fear the flame, she became the fire.”

Anderson is in no way a MAGA mega donor. Her one GOP donation seemed to be in 2022, giving $2,800 to Florida Republican Maria Salazar.

Guilfoyle was reportedly “blindsided” by the news Don Jr. was hanging with Anderson.

Anderson — whose father was banker Harry Loy Anderson Jr., and whose mother, Inger, was a favorite of famed photographer Slim Aarons — has started posting pro-Donald Trump content on her Instagram feed over the past month, according to a source. 

A source tells us of Guilfoyle’s relationship with the Trumps, “The family doesn’t like her.” 

But another insists that isn’t true. “I’ve heard the president talk about Kim in private many times, and it has never been anything but positive,” they told us. “All of this seems overblown.”

Back in December 2022, Page Six had heard the same rumors, that, “The vibe is that the family doesn’t like Kim. She is trying too hard to be in the family.”

Eric Trump, however, told us at the time when we reached out for comment, “I completely disagree with the narrative and happen to think the world of Kimberly.”

The pair began dating in 2018 and got engaged in 2020. Guilfoyle was previously married to California pol Gavin Newsome, and design exec Eric Villency.

This week, the Palm Beach Daily News (locally nicknamed, “the Shiny Sheet”) wrote in their print edition that their spies also spotted Anderson and Trump Jr., (though the online version leaves it as a blind item).

“The pair recently put on a poolside show of PDA at a local club that convinced all watchers that A) Kimberly is history; and B) somebody is getting a no-PDA letter from the club,” read the article.

A local source tells us that may have been referring to the Beach Club or the Breakers, since other clubs with poolside dining are still closed for the season. (Honor Bar does not have a pool.)

Reps did not respond to requests for comment.