How to submit Harvard-specific supplementary recommendation

My “other recommender” wrote a letter for me through Common App during the early admission cycle to Stanford University. It was a letter that mentioned Stanford by name, so obviously it can’t be sent to Harvard. However, I want to have the same recommender write a supplemental recommendation letter for me to Harvard.
When I add her as an “other recommender” for Harvard, the Common App doesn’t give me the option to send a new recommendation request to her for a new letter. It just uploads the letter she sent to Stanford. I can’t delete and re-add her to my recommender list because she already completed the form.
Does anyone know how I can have the same recommender send a new recommendation letter to Harvard when a letter was already put into Common App under that recommender’s name?

Once you submit your Common Application to a college, you cannot change it – just as if you had sent it in the mail. You can upload the other recommendation letter to the portal, or have your recommender snail-mail it to Harvard (or another school).