On Facebook how can my friends see comments I have made on other friends pages if they are not their friend?

[pri✍]

Your sister will for sure see your comments/likes to anything if she put you in her Close Friends list.
She might also see that in her tickler.

If your friend has Follow button:
• and set it to allow comments from follower and the post is set to Public ➤ she can comment/like your comment, even she can comment/like that post;
• but set it NOT to allow comments from follower and the post is set to Public ➤ she can only like your comment, even she can like on that post.

Otherwise, she can only see it UNLESS the post is tagged to friend (eg. you) that is your sister's friend, she can comment/like the post and of course she can like your comment.

Complicated? If you grasp the basics, it's not that complicated.