A Newfoundland woman says she's feeling "betrayed" after her $100 "Roll Up the Rim" prize was claimed by someone who saw a photo of the winning cup on Facebook. However, Tim Hortons said it will still honour her prize, and is now investigating the incident.

When Margaret Coward, of Conception Bay South, N.L., rolled up the rim of her Tim Hortons coffee last Friday, she was ecstatic to see that she'd won a $100 gift card.

After notifying her husband and children of her luck, she happily snapped a photo of the winning tab and posted it to Facebook.

"Woohoo, I'll take that," she wrote in the online photo caption.

However, just a few hours later, she realized that sharing a photo of the winning tab was a mistake.

Coward told CTVNews.ca that she had won prizes in the "Roll Up the Rim" contest before, but had always submitted her tab through the regular mail. Some tabs include a unique PIN code that allows winners to claim their prize online.

But when Coward tried to claim her gift card online, she kept getting a message that the claim was "invalid." After contacting the company to see what was wrong, she learned that someone had already used the PIN code to claim the prize before her.

Coward, who works as a school secretary and has three children, told CTVNews.ca that she felt "betrayed" that one of her Facebook "friends" was likely the person who stole her prize.

"Be careful of what you post," she said in a phone interview, noting that she purposely set her Facebook privacy settings so only her accepted friends can see certain photos, including the photo of the winning cup.

"You wouldn't stop to think that this would happen. Had I known that this is what the PIN code was for, I never would have posted it," she said. "As well, sometimes your 'friends' aren't really your friends."

And while she can't say for certain who the culprit may be, she noticed that she lost one Facebook friend after she shared news of her ordeal online.

Coward posted about the incident on Facebook to send a warning to other Tim Hortons lovers to watch what they share on social media.

"Goes to show you that you always need to be careful of what you're posting and taking pictures of," she wrote in her post. "Something I so excitedly and innocently posted … always a lesson to learn, even at my age."

On Monday afternoon, after her story went viral, a Tim Hortons customer service manager contacted her to let her know that the company would still honour her prize.

"He was very nice and he listened to the recordings from Friday when I contacted them just after I won and was trying to redeem it online,” Coward told CTVNews.ca in a message.

The company also said they would be investigating the incident, she said.

Looking ahead, Coward says she plans to use her new gift card to take her family, as well as a few good friends, out for a treat.

"Of course I'm going to take my family out," she said, laughing. "And I have a few really, really good friends that have told me to stay strong, don't worry about it, and 'We're here to support you.' Those four or five friends, we're going to go out and have a nice coffee.

"That coffee's going to be on me once I get my card."

In an email to CTVNews.ca, Tim Hortons Director of Communications Jodi Bond said the company introduced the PIN code feature to allow winners the chance to collect their $100 TimCard prize online.

“As these are unique PIN codes, we do not encourage our guests to post images of their tabs on social media until they have redeemed their prize,” Bond said.