Kozel, 41, of Medina, Ohio, spoke with ABC News on Monday about the incredible feat, which was made all the more amazing because she is paralyzed from the waist down and because she says she hiked the trail with the help of braces.
Earlier this week, her story was featured on various news outlets, including ABC News' "World News Tonight," sparking interest within the Facebook group Pacific Crest Trail Class of 2017. Some members of the group raised questions among themselves, asking whether hikers who'd been on the trail during the same time period as Kozel remembered seeing her.
Kozel said she started receiving messages Wednesday, inquiring about details from the hike and accusing her of lying about completing the journey.
Donna L-Rod Saufley, who owns a hostel along the trail and was described by member and two-time Pacific Crest Trail thru-hiker Mark Votapek as "the most famous trail angel on the PCT," started the group thread Wednesday, writing: "Did anyone in the Class of 2017 see Stacey Kozel on the trail this year?"
Saufley, responding to all the media attention the disabled hiker was getting, called Kozel's claim "unbelievable and frankly ridiculous."
Saufley and her husband have hosted Pacific Crest Trail hikers for more than 20 years at their Agua Dulce, California, home. Their home is situated at mile 454 and this year, she said, her two-acre hostel -- called Hiker Heaven -- had hosted more than 1,500 hikers on the trail.
She said the two are members of a "trail angels" group that communicates with each other and keeps tabs on the hikers. Saufley, who described herself as a trail section hiker, also completed the Pacific Crest Trail around the same time as Kozel. She said she had not heard of Kozel from other hikers and that had given her initial pause a few weeks ago.
"The trail grapevine is incredibly robust, so even if she didn't stay at Hiker Heaven, surely I would have heard about her. I spent time on the trail this season too, and saw many hikers on my journey. I finished the trail at the northern terminus around the same time that Stacey claims to have been there. No mention of her at all from anyone," she said.
Chatter about Kozel took over the Facebook group's conversation.
Saufley shared some of the information and speculation that members of the group had put forth to discredit Kozel's hiking claims.
According to Saufley, snow levels, flooding and fires made it "nearly impossible for able-bodied" hikers to complete the trail this year. She said that not one trail angel along the Pacific Crest Trail had reported seeing, hosting or helping Kozel. The group also took issue with Kozel's hiking dates.
"The dates Stacey has provided do not add up. She says she is 'slow' but claims to have done a contiguous northbound thru-hike in what would be considered an extremely fast pace," Saufley said. "The dates are all over the place; she says she started on several different dates, and the same is true about her finishing date. ... There is one fact that most thru-hikers remember: the dates they started and finish the trail. No one is ambiguous about their dates. Except Stacey, who can't seem to decide when she started or finished."
"Rather than respond with facts, photos, or people that Stacey met along her journey, she instead took all her accounts offline after questions about her began to surface. Not one shred of evidence has been put forth that validate Stacey actually being on the trail, by Stacey or anyone else," Saufley said.
The Pacific Crest Trail Association today told ABC News that while it was aware of the controversy surrounding Kozel, it did not get involved in disputes over hikers or whether they hiked the trail. It said completion of the trail was based on an honor system.
"There is no requirement for anyone to report their hikes to us. … We don't validate or verify hikes in any way," said Scott Wilkinson, the association's director of communications and marketing.
When contacted by ABC News about the accusations, Kozel told ABC News that she was "heartbroken" over what was being said about her online.
"This was never about doing a thru-hike for me," she said. "It was more about 'not giving up.'"
She told ABC News that she had taken two trips off the trail, flying to speaking events in Ohio and then West Virginia. She maintained, however, that she'd returned twice to complete the trail end to end. She said she doesn't have witnesses to vouch every step of the way.
Addressing those who say she finished the hike too quickly, Kozel told ABC News that she "pushed through much of Washington at night" because she couldn't sleep well due to the cold temperatures, which gave her muscle spasms.
Many nights, instead of setting up her tent, she said she would sleep outside without overhead protection for a few hours at a time and then push through with more hiking to keep herself warm and free from spasms. Near the emerging fires, she says she quickened her pace to avoid them.
Kozel said that many of the people raising questions were trolling her and leaving nasty messages so she'd closed her social media pages. She said she couldn't read the messages because they were so hurtful. She also said she didn't want to respond to them because she felt that would only "add fuel to the fire."
Kozel has since deactivated her social media accounts and taken down her website.
She released a statement late today, saying in part: "Earlier this year I hiked the Pacific Crest Trail. I hiked it to challenge myself, to push myself to the limits. I did it for myself, for no monetary gain, or media attention. I did it because I needed to do it. ... I hiked the Pacific Crest Trail."
In 2016, Kozel says she hiked the 2,190-mile Appalachian Trail. She said that she had not faced any accusations about that hike. On the Appalachian Trail, she said people were looking for her along the route. On this trip, however, she said she wanted to be more low-key and not too noticeable.
"My reputation is on the line," she said about the accusations. "My integrity is on the line."