The mother is a witness in the lawsuit filed by Mueller over the loss of his job.
Ms Swift, 27, accuses broadcaster David Mueller of slipping his hand under her dress while they posed backstage together at one of her 2013 concerts.
Swift is countersuing Mueller, claiming sexual assault.
On Tuesday, Mueller testified that one of his radio station bosses, Hershel Coomer, said he had met Swift earlier before the show and that "he told me that he had his hands on her butt".
Mueller's lawyer, Gabriel McFarland argued, "if you look at that photo, his hand is not underneath her skirt".
David Mueller, wearing a dark suit, sat Monday at the plaintiff's table with his back turned to Swift, who sat at a nearby table with her mother, Andrea Swift, and their attorneys.
Taylor Swift's legal team planned on Wednesday to resume cross-examining the Colorado radio personality accused of groping the recording star during a photo shoot four years ago, an allegation the former DJ vehemently denied under oath.
Though several fans showed up for the trial, public interest in watching it at the downtown Denver courthouse is lower than expected, according to the Denver Post, which said that public seats to view the trial in an overflow room were handed over to the media. She "not trying to bankrupt this man", said Swift's attorney.
He is seeking financial damages from Swift, who countersued him for assault and battery.
Mueller said in depositions that his damages amount to some $3 million. "A woman gets assaulted, a woman reports it, and she gets sued", Baldridge asked jurors. Fans lined up outside the courtroom holding tokens, hoping to catch a glimpse of the star during the nine-day trial.
Under cross-examination on Wednesday as part of a federal civil trial, former KYGO radio host David Mueller testified that the photo of him and Swift from 2013 appeared "weird" and "awkward".
A key piece of evidence in the case is the photo in question of Swift, Mueller and his then-girlfriend, Shannon Melcher, from the meet-and-greet.
Following the opening statements, Mueller, who made $150,000 a year at the radio station, denied in his testimony that he was seeking that much money.
"She couldn't believe that after he grabbed her, that she thanked them for being there", she said.
After Swift came forward about the incident, Mueller was sacked from his job at the country music station, despite coming forward with his own version of events.
But he also said that in the meeting Haskell and Call had called the next day, that he never told Call about what he says Haskell told him.
Taylor Swift playing the first of two sold out shows at the Pepsi Center on her most recent tour for the album 1989.
Swift's security team then approached Mueller, accused him of inappropriately touching the singer, and asked him to leave the arena. Court documents say it is unlikely that either side will settle.