What are the most important things you look for in a shoe, besides style and fashion?
It has to fit well, it has to be comfortable and dependable.
What the father is saying is that Rachel can always be depended upon, that she makes herself fit other peoples wishes.
It also says that she is not particularly noticeable, she doesn't stand out.
Rachel doesn't want to be thought of as just someone who is dependable, but that nobody gives much notice to.