A wedding guest has been criticized by the groom's mother after she was caught eating food she brought herself to the wedding.

Sharing her story on Reddit, she explained she was at her university friend's nuptials when the groom's mom confronted her in a diet-shaming rant.

"She confronted me and said I was 'embarrassing the family,'" the 36-year-old said in her post.

The guest said she was initially "excited" to attend her mate's wedding but was aware she had a "medical condition" that meant she couldn't eat gluten or dairy.

She didn't specify her condition, although people with coeliac disease react negatively to gluten, which can damage the small intestine, and lactose intolerance makes digesting dairy difficult.

"It's not a fad diet or preference, I get very sick if I eat them," the guest added, noting she had made her dietary needs clear when RSVP-ing.

Despite this, the bride told her that the venue couldn't guarantee food that was completely gluten or dairy-free due to cross-contamination, but she hoped she'd be fine just eating "salad and fruit."

Not wanting to cause a fuss, she discreetly packed a small container with grilled chicken and rice to eat at the event.

When dinner was served, she slipped out for five minutes to eat, then returned to the gathering.

"I didn't make a fuss, didn't bring any smelly food, and didn't take anything away from the event," she said.

Unfortunately, her friend's mother-in-law caught her mid-meal and started badmouthing her to other guests, saying she was "disrespecting the caterer" and "making the couple look cheap."

She even told her directly that she was embarrassing the family and should have eaten before the wedding if she was so worried.

The Reddit user also said the mother-in-law criticised her for eating near the wall on her way to the bathroom, saying she looked "like a homeless person."

She explained her medical condition necessitated special arrangements to avoid getting sick, but the mother-in-law rolled her eyes and called her selfish. The mom also claimed the wedding was "about the couple, not about your dietary needs."

Some of her mutual friends even agreed she was in the wrong, saying she made an "a-hole move" that reflected poorly on the couple.

However, commenters mostly supported her actions.

"You took care of your own needs," one said.

"Is it somehow respectful to eat foods that would physically harm you? LOL. No," another replied.

Someone else accused the groom's mother of "looking to stir trouble where there isn't any."

"If I were the bride, I'd be watching MIL closely," one warned. "Since the poster is a friend of the bride, this could be a sign of trouble down the line."

Another thought the bride shared some blame, saying, "Yeah, the bride didn't seem too worried her friend would have enough to eat. She gets some side-eye from me for that."

Friend slammed by groom's family for 'selfish' act on the...