Would you please tell me what was the best course of action I could take at the time?

After completing over 120 credits, including 5 of her courses with A- or B+, a professor said to me, "if you drop that course, I don't have confidence to write you the letter of recommendation." I completed the course with A. All the while, I kept telling her how risky it was for me to be burdened with an extra course at the term that was likely to be my only opportunity to apply to graduate school for actually attending it. After all, she didn't write the letter. Some guy said to me that the professor wanted to protect her reputation by not writing me the letter. I don’t think that was the case here. She had written a letter to a US Consulate General in Japan to recommend me for student visa. It was probably because I questioned her common senses: I asked her if she knew admissions process, or precisely international admission process, and to be honest with me if not because she could be misleading me. Her umptions on graduate school often contradicted what I was actually told by them: in many liberal arts schools, financial aids were generally unavailable to incoming international graduate students who pursued only mater’s degrees. Financially, I was at my limit, but she was telling me to take on more courses. How can you go to graduate school if your bank account is empty and loan is not an option? Furthermore, considering the term is likely to be my only opportunity to apply to graduate school for actually attending it, if I don’t get in a graduate school, what is the point of all those undergraduate years? Racial prejudice, not racial discrimination, might have played a role too. I was a small, immature-looking guy who spoke English with a very heavy Japanese accent. Because of these features, I might have impressed her as academically immature no matter how well I did in a course. I was a double major and completed over 140 credits at the time of graduation. The professor was my academic adviser of 5 years and the only professor who was specialized in the discipline of my primary academic interest. I was an international student on a student visa. Under current immigration laws, international students must go to school without interruption in order to keep it valid: if I didn't go to graduate school in the semester immediate after graduation, I would lose my visa. The best course of action I could think of at the time was to drop an unnecessary course and concentrate on making my application strong, primary polishing my personal statement and writing sample, which I didn’t. In fact, other professors who were also my recommenders kept urging me to rewrite the personal statement and one of them later said to me that grades weren’t the single most important factor of the application, which I already knew. In the end, my opportunity to go to graduate school was wasted. The failure was mine. However, the fact that the professor considerably disturbed my endeavor remains unchanged and, even today, it still bothers me.