Larissa took to the local Fubar News page on Facebook to thank service section leader and first-aider Joy Johnson, front-end colleague Nikki Milne and pharmacy colleague Michelle Stewart together with customers for their "amazing and kind" efforts looking after Penny.
She said: "I'd just like to thank Joy and everyone from the bottom of my heart for what they did. They were amazing; such lovely ladies."
Larissa called into Asda to do a food shop after visiting neighbouring stores and, as Penny seemed tired, put her in a trolley where she promptly fell asleep.
She said: "I just got on with my shopping and Penny didn't show any signs of not being well. She was just sleepy, which is normal for her. I was just going down the last aisle before I got to the till as I was doing the Scan & Go and she started to make a really funny noise.
"I picked her up out of the trolley and she had gone a really funny almost blue colour. Penny has a history of intense febrile convulsions and can stop breathing. I felt how hot she was so started to strip her down to her nappy. A customer came over, asked if everything was okay, and sat on the ground with me while her friend went to get help.
"Joy and Nikki came over and Michelle said for us to go into the consultation room. Penny had been quite sick at that point and this in when Joy really stepped in.
"Penny kept coming in and out of consciousness. It was really scary, I thought she was going to die. Joy said she wasn't happy and phoned for an ambulance and stayed with us till it arrived. It took after 30 to 40 minutes, but it felt like forever.
"Joy could see that I was under a lot of stress but she just kept calm. She was holding Penny and was just so lovely. Such a lovely, lovely person.
"I phoned my mum at this point to come over to finish off the shopping as I've got three older children who all needed feeding, but she had never done Scan & Go before so Nikki did it all for her. She was really good. She waited outside after her shift for the ambulance as she wanted to see that Penny was okay."
Penny was taken to Aberdeen Royal Infirmary and, after being checked over, was allowed home. She has been referred to paediatrics for further investigations.
Joy, who's worked at the store for seven years, said: "When I first got to her Penny didn't look too bad. Her mum had stripped her off and was cooling her down with water. But after about five minutes or so she started to drift in and out of consciousness. Her colour left her and she was incredibly pale. At that point I said that we should ring an ambulance as Penny had a wee bit of history of having febrile convulsions.
"While we were waiting for an ambulance I was comforting and reassuring Larissa and kept encouraging Penny to open her eyes and 'look at this' just to make sure she was still alert and responding to voices.
"It was an eventful afternoon and it was so nice to hear that Penny got home that night and was doing okay. It was a huge relief."
Joy, Nikki and Michelle have now been nominated for Asda service superstar awards for their actions, with store manager Martin Green saying: "We are all very proud of them.
"They just did what they had to do with no fuss, they just got on with it. Their actions went above and beyond and we are all glad that Penny is doing well."