It clicks quickly, sharp as she is. Her mouth opens, closes, opens, closes. Opens:

"Oh no."

She sucks in a breath. "Oh dear - wait - wait, are the two of you...?"

Are they together? Or just friends? Or are they friends, because they don't have to words for the whole thing? Maybe wherever they're both clearly from doesn't accept two men together. It's not as though everywhere in Hermione's world does, even if she has no problem with is. But if they're together, then she shot herself in the foot a lot harder than she thought.