Amanda Serrano retained her undisputed featherweight titles with a unanimous points decision over Heather Hardy in Dallas.
Puerto Rican Serrano, 34, landed almost twice as many blows but praised her 41-year-old friend after judges scored the bout 99-91, 100-90, 100-90.
“Heather is a hell of a fighter. She’s as tough as they come,” she said of the her fellow Brooklyn-based boxer.
Serrano’s manager, YouTuber Jake Paul, beat former UFC fighter Nate Diaz.
Serrano has signed with the Professional Fighters League to compete in MMA, along with Paul, and refused to call out future opponents after her victory.
She became undisputed featherweight boxing champion with a win over Erika Cruz in February that set up a potential rematch with Irish fighter Katie Taylor, who won their lightweight contest last year.
But the Puerto Rican withdrew from the rematch with injury, and Britain’s Chantelle Cameron stepped in to inflict Taylor’s first professional defeat.
Paul, who has more than 20 million YouTube subscribers, was on the same the bill against fellow American Diaz at the American Airlines Center.
In his eighth professional fight, he bounced back from his first defeat against Tommy Fury in February.
The 26-year-old knocked Diaz – making his pro boxing debut – to the canvas in the fifth round of their 10-round contest.
But he was made to work for his unanimous points victory by the 38-year-old Diaz, who left the UFC after 15 years in 2022.
Paul, who won 97-92, 98-91, 98-91 on the judges scores, has made a $10m offer to Diaz for a fight under MMA rules.