Maya still seems to see herself as a lesbian at heart. At the picnic, she's worried liking boys will turn out to be a delusion; she does not voice a similar worry about girls. This is backed up by her conversation with the MC prior to her sex scene in Episode 5 where she says she can be herself around the MC and still have him understand her:
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Note the plural, girls. To me, this suggests that Maya has been attracted to other girls in the past, even if Josy was the only one she actually slept with. Whereas Maya had felt no connection to the boys she had dated prior to the MC. Hence she is confident she likes girls in general, and is just not sure whether her attraction to the MC is a flash in the pan, a singular exception, or an indication she really is bi.
Obviously, whatever we choose to classify Maya as, she's someone who cares at least as much about an emotional connection with a potential lover as she does about the chance to have sex. But for now I'm willing to accept that she is more likely to have that connection with girls than with boys.