I think Maya was effed up even before the resets. She implies that Sensei and her were "pretty fucked up" and that's why they got attached to eachother:
There's also some implications that she may have been raped by a family member, and was homeless before meeting Sensei.
I think the "girl who never made it home" story told by Sekai in 'Something Everyone Knows and Ignores' may have been about Maya:
Mostly due to the vending machines and running into a stranger parts:
Which could be why Maya takes Sensei to a vending machine and buys him the drink that makes him nostalgic:
There's also the implication that someone else took Maya's "purity" in 'The Room with Clocks':
before Sensei could adopt her and show her "true love". (Unless that black figure is the old Sensei, but that seems unlikely)
I also think this is from Maya's pov due to the green scarf:
The "finally be happy" and "finally knew what it meant to be loved" parts, makes me think something must have happened to her.
Nevertheless: Current Maya is considered "Broken beyond repair":