The speaker watches an old friend smile and, almost against their will, smiles back. But the warmth is complicated. The two used to be best friends, and now the friend is with the man the speaker once loved. The poem never says how that happened, and it doesn't need to. The distance between them says enough: "times have changed."
What stands out is how gently the speaker handles the hurt. There's no accusation or anger here. Instead the speaker wishes the friend well and hopes she won't be hurt "the way i did." That last line is where the pain slips through. It's kind, but it also hints that the relationship ended badly for the speaker, and perhaps that the speaker doubts it will go well for her friend.
The mood is bittersweet and restrained, a mix of generosity, loss, and quiet sadness. The short, plain lines and simple wording make it feel like a private thought, spoken honestly and without drama.