She left without complaining, not wanting to cause a fuss for fear of ruining a much-needed family holiday .
For months Jenny had been concerned about Billy as he appeared to have little strength as he walked, and had been vomiting all his milk as they attempted to get him onto solid food.
But doctors dismissed her worries, and said it was just a problem with weaning.
The shop worker's cruel comment about Billy stuck in Jenny's mind and it was not until she mentioned it to a health visitor that the jibe ended up saving the tot's life, as he was finally diagnosed with a lethal brain tumour.
“Over the past few weeks, we’d noticed he looked like he was staring, but I never dreamt it could be a sign of anything sinister," said Jenny, 37.
The family had been out Christmas shopping when a male shop assistant started looking awkwardly at Billy.
Jenny said: “He just stared and then blurted out: 'Your baby’s eyes are freaking me out! They’re scary'.
"I was shocked and couldn’t believe he’d say something so cruel about my baby. Craig and I just looked at each other lost for words. Isla and Poppy were with us, too and we didn’t want to spoil a family day out."
Jenny lives in the Wirral, Merseyside with partner Craig Moss, 31, who is Billy and three-year- old Isla’s dad, as well as Molly, 17, Jake, 13, and Poppy, nine from her ex-husband.
At the time Billy had been looking downwards and you could see the whites of his eyes, but his family never thought this could be an indication of a life threatening tumour that gave him just a one in four chance of survival.
When her health visitor came round a few days later, Jenny showed her Billy’s eyes.
“She took one look at him and said he had ‘sunset’ eyes, which was a sign of build-up of fluid on the brain,” added Jenny.
“Then she told me I needed to get it checked out urgently.”
The health visitor rang the Wirral’s Arrowe Park hospital, who said to bring Billy in.
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