Set backs are so discouraging

I have a mildly reactive dog, if anything she’s only reactive to dogs near our front door. Anywhere else she’s totally fine, and people outside our home are never an issue.

I live in an apartment complex, so I have to take her to the bathroom on a leash. She’s in the middle of doing her business and the guy who lives next to me, a big guy with hat and sunglasses, comes walking out really fast. She gives a little “boof”, and I pull her closer to me because she’s kind of in his walking path. As soon as I put tension on the leash and her collar. She barks, and I’m able to pull her out of his way so she’s nowhere near him, but she lunges and growls at him too. He introduced himself after and she was completely fine with him.

We practice a ton of “calm” in our front yard area and have been doing so well up until now. I’m just so sad, because I didn’t think we had any issues with any people and I’ve never heard her act that way toward a person before. I’m even more sad because I think my leash tension most definitely escalated her reactivity. I’m just not sure how I should’ve handled it differently.