You have identified that friendship skills are important social skills for her to work on now. The first step in teaching these skills is to introduce them to her. Tell her that you are going to help her learn some skills that will help her make and keep friends at school. This will reassure her.
The next step is to identify some of the things that you both feel are important in healthy friendships, such as honesty, conversation skills, fairness, etc. Then make a list of the things your daughter can do to demonstrate that she is honest, has good conversation skills, is fair, etc.
To make it fun, role play. You become the potential friend, and your daughter tries to strike up a conversation with you. Or you can role play that she is in a situation in which she has to tell the truth about what she might have done. Praise her for practicing and using her skills correctly, and give her goals. She should use one new skill a day at school. See how she does.
You might consider visiting the Boys Town Press website at
www.BoysTownPress.org and consider some of the materials. Books and workbooks that focus on various social skills are available. Two such books are
A Good Friend: How to Make One, How to Be One by Ron Herron and Val J. Peter, and
Friends Forever by Fred Frankel. Both books advise kids and parents on such areas as friendship do’s and don’ts. Activities for the two of you to do together are included.