One friend told me that I should order the referees by the (estimated) strength of their letters. She believes it makes a difference since the admission committee would start reading letters in the order you entered the contact information for the referees (i.e. the order you request their letters in the application portal), and the first letter they read determines their first impression of you. As a result, the recommendation from your "first recommender" is more important in the same sense as the first paragraph of your research statement is more important.
I wonder if that is true. In fact, the person whom I listed as the "first recommender" is not the one who would give me the strongest letter. Should I remove her and start over to make sure that my strongest letter will be the first one to be read?