Some people show love or affection through physical touch; similarly, some don’t like physical contact or touching. As you said, that girl is new to your group which means she naturally knows you less than others. In that case, you need to talk to her and explain your situation. You won’t be able to stop her until you tell her that you don’t like to be hugged and that she makes you feel uncomfortable. We would suggest you, do not react aggressively or be harsh on her and communicate very calmly. Effective communication can solve most of your problems.