A woman cries because she already knows how this will go. Whatever the man does, she will forgive him. Whatever she hears about him, she will still describe him kindly to other people. The short, plain lines make her sound worn down, almost resigned, as if she has stopped arguing with herself. The question "What could she do" isn't really a question. It sounds like a shrug, a sign that she feels trapped by her own feelings.
The title, "The Course," suggests love is something you learn, and the last line backs this up. She has "mastered the art of love," meaning she knows how to give, forgive and protect. But she hasn't yet learned what that will cost her. The speaker seems to look on from outside, sympathetic but worried. The mood is sad and quietly uneasy, with a sense that the pain is still ahead of her. The poem leaves us wondering whether loving this fully is a strength or a trap.