The purpose of socialization is to expose your dog to various new places, sounds, social partners, and sights in a positive way. It’s generally more difficult for older dogs to adjust to novelty, though the better the socialization was, the easier it is for them. For those dogs who did not have those good experiences early on in life, learning to accept new experiences and objects while still being comfortable in the world might take more effort, but growth can be made and can continue throughout their lives.
The most important part of making up for lost socialization opportunities is to keep it positive. Your dog can learn to accept new experiences and situations or become less fearful of them by having many positive experiences. For example, if your dog didn’t get to meet children early in their life and now finds them terrifying, they can learn to be okay around children if you begin with a child who’s too far away to upset her. When they see a calm child on the other side of the park, you could give them a piece of chicken? If you do that enough times, and your dog will start to associate the sight of a child with chicken, making seeing a child a positive experience, and that’s great.
Over time, you can gradually have your dog in new and different situations with children, in ways that don’t upset them but instead, continue to teach them to be happy about seeing children. Those positive experiences are critical for success. If you force them to be too close to something or spend too much time in a context where they’re uncomfortable, you will only get in the way of their progress; you will not accelerate it. Ideally, you can keep it positive and know when to quit while you’re ahead, but you must remove her if that fails. It is only kindness to protect your dog from situations that cause her distress. Expose your dog to new things without trying to expose her to the whole world at once. Remember, the goal is a safe and happy dog, comfortable with most of the people and things they encounter in life.