You can't really teach kids how to be social. The best way for them to learn is at their own pace, on their own. Pushing them to be friendly, give hugs, is what we should not be doing. From day one, babies are learning to follow their instincts, learning who and how to trust. They learn who responds when they cry, when they are hungry, need a change, etc. Primitive and basic, but this is serious work and learning for them. As they progress, the process is the same, however, they start looking to their parents, and close family for cues. Even if we just love Aunt Sally, maybe her makeup, her boisterous laughter, might take a little getting used to for a toddler. If we are pushy, we are teaching our toddlers to dismiss their instincts and feelings, and follow ours. Bad idea. Better to let them learn to trust themselves. With much practice and success, they will learn how to make good decisions on their own. The flip side is true. If children don't learn this skill, they will always be listening to others when making decisions, they will be weak standing up to peer pressure. And, they will not trust the most important people in their life, their parents. Better that we build a foundation of trust, guidance, and support while they are small, than try to do that when problems arise as teenagers.
We all know that animals are intuitive and instinctual. We are too, if we don't let our egos get in the way. If she doesn't want to go give Aunt Sally hugs and kisses, don't be embarrassed, just smile and change the subject. It's not about us, it's about the comfort and safety of our little ones. Don't forget that all children are different. If an older child seemed more social, it could be that everyone is different now. Maybe the circle of family and friends was smaller, and now it has grown considerably. It really doesn't need to be explained, analyzed, just allowing the child to be who they are is most important. Little ones think it is all about them, and for the short term it is true.
As a grandmother, I found the most exciting part of watching my grandchildren develop, is watching them figure things out for themselves. One of my favorite memories was when my 7 yr old grandaughter, 4 yr old grandson got into a battle. They were two rooms away, I heard them yelling at each other, then almost simultaneous screams and crying. By the time I made it to the room to intervene, they were both holding each other, sobbing, and both were taking turns saying sorry, no, I'm sorry. I discovered that both of them did something to physically hurt the other, but punishment from me wasn't necessary. They already had it figured out. They learned lessons all by themselves that no one could possibly teach them. These wise little ones can teach us alot!