Plain yogurt is a test taste, not a kitten staple
A weaned kitten can try plain yogurt in a very small amount, and the word plain is doing real work in that sentence. The yogurt in question has one job: milk and live cultures, with no added sugar, no fruit puree, no honey, and no artificial sweeteners. Sweetened yogurts made for people bring sugar a kitten does not need, and any product sweetened with xylitol is dangerous for pets and should never be shared.
Start with less than you think. A lick from a spoon or a teaspoon smeared thinly on a small dish is a fair first trial, given on a day when the rest of her diet stays exactly the same.
Why dairy sits uneasily in a kitten's stomach
Kittens are born able to digest their mother's milk, but that ability fades after weaning as the enzyme that breaks down milk sugar declines. Adult-style dairy can therefore pass through partly undigested, fermenting in the gut and producing gas, cramps, and loose stool. Yogurt is gentler than a bowl of milk because its cultures have already broken down part of that milk sugar, which is why a spoonful may sit fine while milk does not.
Individual kittens vary a great deal. One may clean a spoon without a flicker of trouble while a littermate is uncomfortable within hours, so a sibling's success is not a promise for your kitten. The trial, not the theory, decides.
Serving yogurt the careful way
Bring the yogurt to cool room temperature rather than serving it fridge-cold, which can sharpen stomach discomfort, and offer it separately from her main meal the first time so you can judge the reaction cleanly. Plain full-fat yogurt is a better test than highly processed low-fat versions loaded with thickeners and flavourings.
Never present yogurt as a milk replacement for a young or orphaned kitten. A kitten who still needs milk needs a proper kitten milk replacer from a veterinary source, fed on a young kitten's schedule, and yogurt cannot meet that nutritional job. For a weaned kitten, keep yogurt rare: an occasional spoon, not a daily topper, so her appetite stays aimed at the complete food she is growing on. Serve it in a separate small dish rather than stirring it through her dinner, so a refusal costs her nothing and she never learns to expect a dairy finish to every meal.
Signs the yogurt trial should end
Watch the litter tray for a day after the first taste. Soft stool, extra gas, a gurgling belly, or vomiting after yogurt means dairy does not agree with her, and the experiment is over rather than something to push through with smaller servings.
Contact your veterinarian if loose stool continues into a second day, if she refuses food, or if a very young kitten becomes lethargic, because dehydration moves fast in a small body. If the spoonful caused no trouble, you have learned something useful about her digestion that is worth keeping with her feeding notes.
That is a natural job for KinsLe, where Care Teams keeps the yogurt trial, the amount served, and the outcome visible to everyone who feeds her, instead of relying on whoever happens to remember.