Hello and welcome to the forum.
You may want to go to the introduction forum and introduce yourself and tell us a bit about yourself. How long you have been making soap etc.
Also, many will not be overly eager to share their recipes as we have worked long and hard on our recipes and kind of guard our secrets. However, if you scroll to the bottom of this post, you will see other topics related to your question you may find helpful.
Do you have a recipe in mind? If so, post it and we would be more than happy to help you with suggestions. There are many reasons and things that cause acne/blackheads and what works for one person may not work for another. It takes a lot of trial and error to find what works best from one to another. I know from experience what works for me may not work for your sister.
There is a lot of awesome information and people on this forum always willing to help.:smile: