Joan Smalls isn’t being the bigger person.

We’re told she’s so furious that fellow Victoria’s Secret Angel and former BFF Candice Swanepoel has hooked up with her one-time paramour Tom Brady that she’s giving their mutual friends an ultimatum: you’re either friends with her, or friends with me.

The women had been “inseparable” for 15 years, but are apparently discovering that sharing the runway is one thing — sharing a football player is quite another.

According to our source, when Smalls was dating the Patriots great, Swanepoel gave her a hard time, repeatedly encouraging her to dump him.

But when the opportunity arose for the blonde beauty to make her own play to sack the quarterback, she took it.

Incensed, Smalls seemed to take several public swipes at Swanepoel, who shares two sons with ex-fiancé, Brazilian model Hermann Nicoli.

Smalls, 38, commented on a post about their drama, “Two words: ‘SUMMER HOUSE!’ That’ll explain everything.”

(The Bravo reality show’s most recent season showed Amanda Batula and Ciara Miller’s friendship implode after the former began secretly dating the latter’s ex, West Wilson.)

In other screenshots obtained by DeuxMoi, Smalls labeled Swanepoel, also 38, a “backstabber” when a fan asked if they were not friends.

Joan allegedly responded, “im not friends with backstabbers.”

In a separate now-deleted message, Smalls said there “was no girl code.”

“And the disrespect and carelessness in how they treat you is so unimaginable. There’s no going back. Some people lack humility and moral compass,” she added.

“And the way they gaslight, lie and minimize your feelings is the worst slap in the face after 15yrs or friendship. Not a sorry said or written. Onwards and upwards!!!”

And now she’s telling pals to pick a side.

“Candice has always been exceptionally private about her personal life, with her focus remaining on raising her children,” said Amanda Ruisi, a representative for Swanepoel told us, “She and Joan share a longstanding history and a friendship that Candice will always respect.”

Celebrity gossip account DeuxMoi previously reported that Smalls and Brady dated on-and-off for about a year. A source tells Page Six that Smalls and Brady were never really serious.

Our sources say the seven-time Super Bowl champ — who has been divorced from supermodel Gisele Bündchen since October 2022 — and Swanepoel have been together “for months.”

The insider says that the pair have been together since May after being set up by mutual friends and even Brady’s ex wife is happy for the new couple.

“It’s just so insane and so messy,” our source said.

Meanwhile, a rep for Swanepoel, Amanda Ruisi, told Page Six, “Candice has always been exceptionally private about her personal life, with her focus remaining on raising her children. She and Joan share a longstanding history and a friendship that Candice will always respect.”

Since he and Bündchen, 46, parted ways, Brady — who also shares 19-year-old son Jack with ex-girlfriend Bridget Moynahan — has been linked to Kim Kardashian, Brooks Nader, Irina Shayk, Sofía Vergara, Alix Earle and Yael Cohen, though he’s never publicly addressed any of the flings.

Page Six has reached out to reps for Smalls and Brady, but has not heard back.