Thank you for this question that is quite common to several girls. You are right, some young girls feel ashamed when they hit puberty becuase of the changes they see and feel in their body. But there are also some others who feel proud, which is quite acceptable. Puberty is a natural stage of life. It is a sign that you are not a child anymore, but rather are starting on a path to becoming an adult. This can make an adolescent girl feel ashamed but it shouldn’t. It’s normal.
One more thing is that parents, siblings and neighbors can continue to consider an adolescent girl as a child when she feels she is a grown up, and can sometimes undermine her ideas which can lead to frustration. You should recognise that the phase you‘re entering can feel confusing as your body goes through many changes, both physcial and emotional so you migth want to look for an adult you can trust to give you necessary information. When you have all of the facts to hand about puberty, and are surrounded by supportive people, this will help you not to be ashamed of what you are going through.