I am not sure what was happening in this scenario, but there are slight differences in holding something and holding onto something. Either way you would be understood. Here are some examples: He held onto the rope so he wouldn't fall. She held the baby until he was quiet. You hold your girlfriend because you like her. You hold onto your child so he won't run into the street.

When you say, "Can I change from left to right," do you mean changing Penny and Lynette in the sentence? If so, then no. Not unless you change the verb. Like Susan said, hold on to is different that hold. It has a more imperative and lasting feel to it. If I fall off a cliff and grab on to a tree branch to prevent me from crashing 1,000 meters into the ravine below, I am going to hold on to the tree branch rather than just hold it. In the example sentence, I get the feeling that Penny might be trying to get away and Lynette has to grasp her firmly (maybe by the arm) to make sure she doesn't get away. If the sentence said, "Lynette, holding Penny, put a Kleenex over Parker's nose," it sounds more like Lynette is hugging Penny or Penny might be sitting in her lap.