""You didn't almost lose pretty badly," May said."
Is that a typo? Robin did actually lose, rather than almost losing.
When Robin originally asked the question, she said, "I did lose, and almost pretty badly at that, so I get it if you weren't that impressed." She's there referring to the fact that she nearly lost 2-0 (she had only Charizard left while May had Tyranitar and Floatzel, but then her Charizard managed to take Tyranitar down, despite the huge type disadvantage, and ultimately put a dent in Floatzel as well).
May is responding to that statement, saying no, that wasn't almost a pretty bad loss, that was almost a win
. It's kind of a glass-half-empty situation - Robin feels she only barely scraped her way to a respectable 1-0, whereas May feels Robin was dangerously close to beating her.