She also spoke about addiction: as with millions of other Americans, Floyd and Ross struggled to quit opioids.
She said: "We both suffered from chronic pain".
Prosecutors trying a white former Minneapolis police officer in George Floyd's death put Floyd's girlfriend on the witness stand Thursday in an effort to humanize him for the jury, but her testimony also gave the defense an opportunity to delve into Floyd's drug use.
"When I look at George Floyd, I look at my dad, I look at my brothers, I look at my cousins, my uncles, because they are all Black", testified Darnella Frazier, who was 17 when she recorded the cellphone video of the May 25 events and posted it on Facebook, igniting a national reckoning over racism and police abuse.
The defence has argued that Chauvin did what he was trained to do and Mr Floyd's death was caused by drug use, heart disease, high blood pressure and the adrenaline flowing through his body.
Mr Floyd was 6ft 4in and 223lbs, according to the post-mortem examination, which also found fentanyl and methamphetamine in his system.
Ms Ross, who took the new drugs herself, described them as a "stimulant". Medical experts have said that although the level of fentanyl in his system could be fatal to some, people who use the drug regularly can develop a tolerance to it.
He is accused of killing Mr Floyd by kneeling on his neck for 9 minutes, 29 seconds, as he lay face-down in handcuffs. The footage of the arrest prompted widespread outrage, setting off protests across the USA and around the world.
She also acknowledged they both grappled with opioid addiction.
However, prosecutor Matthew Frank tried to downplay the potential toxicity of those pills, getting Ross to agree that, obviously, neither she or Floyd had died from ingesting them in March or May.
'Addiction.is a lifelong struggle' George Floyd was 46 when he died. "It's not something that comes and goes, it's something I'll deal with forever".
They had their first kiss in the lobby that night and, but for the occasional break after a lovers' quarrel, were together until his death, she said.
She said Floyd had been hospitalized for several days in March 2020 for an overdose.
Ross said she and Floyd each had prescriptions for pain relievers but sometimes they got pills on the "black market".
Asked if that was the beginning of their relationship, Ms Ross smiled and said: "Well, not that part". Nelson reminded her that she has previously told Federal Bureau of Investigation agents that the pill made her feel like she was going to die, although she said she didn't recall saying that to the agents.
Nelson then asked Ross if she learned what caused the overdose.
In some of the video, Floyd can be heard calling out, "Mama!" repeatedly and saying, "Mama, I love you!".
"May I tell the story?" she asked.
Although his partner was closer to Floyd, Bravinder said that from where he stood, "I didn't see any breathing or movement". They tried to stop using the drugs many times and had sought out various treatments, she said, but they relapsed together as recently as March 2020.
The call that brought an ambulance to the corner of 38th Street and Chicago Ave.in south Minneapolis was a "code 2 for someone with a mouth injury", Bravinder said. "In my mind at least, we wanted to get away from that", he said.
Chauvin's lawyer has argued that the police on the scene were distracted by what they perceived as a growing and increasingly hostile crowd.
Video was shown of the clerk, Chris Martin, and Floyd inside the Cup Foods store.
Ms Ross first met Mr Floyd in August 2017 at a Salvation Army homeless shelter, where he worked as a security guard. After noticing that she seemed to be distressed, he asked her, "Can I pray with you?". She said: "It's one of my favourite stories to tell".
She said there would be times when he would be up and bouncing around and other times when he would be unintelligible.
"Floyd has this great Southern voice, raspy. He was like, 'Sis, you OK, sis?'" Ross recalled.
"Please, I'm not that kinda guy", Floyd continues pleading.
"It's been nights, I stayed up apologizing and apologized to George Floyd for not doing more, and not physically interacting, and not saving his life", Darnella Frazier, the teen who recorded the video of Floyd's death that went viral and inspired millions to protest, said at the trial on Tuesday. "At the time I had lost a lot of faith in God".
Minnesota is a rarity in explicitly permitting such "spark of life" testimony ahead of a verdict.
Earlier today, jurors heard testimony from Floyd's girlfriend and a Minneapolis paramedic who provided medical aid to Floyd.
Bystander and police bodycam video showed officers pulling Floyd from his SUV at gunpoint, then struggling to put him in the back of the squad vehicle as a panicky-sounding Floyd writhed and cried, "I'm claustrophobic!"
He described arriving on the scene and seeing Floyd's "limp" body on the ground as three officers, including Chauvin, remained on top of him.