While you can try to keep offering it, (she’s likely to spontaneously decide that she likes it again) a good idea would be to try alternatives. For example, if she’s gone off milk, try offering her yoghurt or cheese.
Sometimes, your toddler will decide that she doesn’t like a group of foods, such as fruit. Instead of pushing the issue, simply substitute the fruit she usually eats with vegetables, or try other forms of fruit, like fruited yogurt or dried fruit.
If all else fails, and you’re worried that your child is missing out on important vitamins and minerals, try disguising foods that she’s decided not to eat. Pour cheese sauce over vegetables, or add them to a homemade pizza. Dress up milk by turning it into a milkshake or smoothie, or add foods she’s not eating to soups or baked goods.