What Mahiro was saying to Saki could be directly translated to “Are you like ‘that‘ ?“ . Instead of “that” (referring to thing in Japanese, and romaji is koto), Saki misheard the word and interpreted it as “people” (romaji is hito in JP).
koto and hito does sound alike in Japanese, and that partly explains why Saki misheard.
Also, the nuance in Japanese sometimes makes the true meaning difficulty to convey as well… Mahiro meant to ask Saki: are you like that? (Undertone: are you trying to be friends? )
However, Saki was too afraid to be found out and outed as gay, that she thought Mahiro was saying “are you like those people?” which implies those who are into girls.