The fact that he throws the rest of his alcohol back like that confirms it for her, even without him going on to verbally do so.

"I see," is as she says, mulling it over in her mind. She doesn't think Duo would appreciate outright shows of pity or sympathy, so Mipha saves her sympathetic look for the inside of her cup. "Thank you for telling me. I'm sure it's hard, and... You don't have to tell me more if you wouldn't like to."

She goes quiet a moment, thinking, before she offers, "shall I tell you something about myself too, to make it even?"