Fontaine's body was recovered from the Red River on Aug. 17, over a week after she was last reported missing.
The teen had run away from her home on the Sagkeeng First Nation on July 1 and ended up in the care of a Winnipeg child and family services (CFS) agency. But she ran away from her placements numerous times.
The 18-year-old girl, who CBC News is calling "Katrina," says she met Fontaine while she was heading to a West End Winnipeg convenience store sometime between 10 p.m. and 11 p.m. on Aug. 7.
"I just seen her sitting there and she looked young, so I just started talking to her, and she was under the influence," she told the CBC's Caroline Barghout.
"We just hung out for a bit and that's just how I met her."
Katrina said they hit it off right away and they spent most of the next three days together. She said both of them knew what it was like to be in CFS care.
"I knew the feeling of being alone — like emotionally and mentally when you, like, have nobody — and I guess that's where we connected," she said.
Came into contact with police
Katrina said in the short time they were together, Fontaine had come into contact with several different authorities, including CFS and Winnipeg police.
On Aug. 8 at around 2:30 a.m., the pair visited the Macdonald Youth Services emergency shelter on Mayfair Avenue to grab something to eat and use the bathroom.
Katrina said she asked staff at the shelter to keep Fontaine overnight, but they let her go because Fontaine didn't want to stay there and she wouldn't give them her real name.
About an hour later, the teens came into contact with Winnipeg police officers near Ellice Avenue and Furby Street.
"We were just hanging out and then some guy flagged her from a truck," Katrina recalled. "I thought she knew him or something, I don't know. But she went to go get in.
"The cops happened to be driving by, so I pointed right away," she added. "Then they went and chased the truck down and they told her to, like, walk away."
That incident resulted in the Winnipeg Police Service launching an internal investigation after it was revealed that the two officers had let Fontaine go even though she was known to be missing.
Police Chief Devon Clunis told reporters on Thursday that the officers came across Fontaine during a traffic stop. She was in a vehicle being driven by a man who was allegedly drunk, he said.
Checked in at a hotel
Katrina said she lost track of Fontaine for some time after the police incident but ran into her again at around 8 p.m. on Aug. 8.
According to the teen, Fontaine told her she had been partying with friends before passing out in a back lane behind Ellice Avenue.
Someone called 911 and Fontaine was transported by ambulance to a hospital, where she came into contact again with CFS staff.
Thelma Favel, Fontaine's great-aunt and caregiver, told CBC News she received a bill of $500 for that ambulance ride.
Instead of taking Fontaine to a locked facility, the CFS workers checked Fontaine in at the Best Western Charterhouse Hotel, where she was allowed to leave, Katrina said.
"She just told me that, like, she ended up in the hospital, she was supposed to be at the Best Western placement, and she said that they were going to report her missing if she wasn't back at a certain time," Katrina said.
"I looked at my phone. I was like, 'Oh shit, you're going to be missing in, like, two hours.'"
Katrina said they hung out until about 3 a.m. on Aug. 9, when a man approached them on Ellice Avenue and offered to pay Fontaine money to perform a sex act.
The friend said Fontaine accepted the offer and told her she would be back in about 15 minutes.
Katrina said she followed Fontaine and the man for a block and a half, but it was too dark to see where they were going.
"I don't know, just something didn't feel right," she said. "I waited half an hour, and then time just kept on passing."
Katrina said she even solicited the help of strangers to help look for her friend.
Fontaine never returned. Eight days later, her body was found in a bag in the river. Police are treating her death as a homicide, but no arrests have been announced to date.
"I couldn't believe it," Katrina said, recalling when police told her the news.
"I was like, 'Are you guys sure it's her?' And they kept saying, 'Yeah,' but I didn't really believe them."
Since that day, Katrina said she has been looking out for other at-risk girls on the streets and doing what she can to get help for them, in the hopes she doesn't lose another friend like Fontaine.
"She was just really sweet," she said of Fontaine. "She seemed innocent, still."