Definitely agree with that. It's just the way she's written. Her characterization. She simply believes what people tell her. She doesn't want people to get involved in her personal issues unless they're close to her.
Personally, I believe she's told Sage the bare minimum; Sage asked about why she wanted the free tuition, Maya gave her the breakdown of exactly what she's facing. She probably didn't give Sage any insight into her sexuality or relationships, and just mostly described the loan situation she's trapped in currently. After all, Sage was persistent enough to even visit her in her dorm and open up to her, thereby gaining some of her trust, resulting in Maya being able to explain her problem to Sage since she wanted to know after all. They might've had a discussion on possible solutions, and I'm thinking it might've involved Sage's family (not really sure since it was one sentence and it was vague). Good thing is, Maya seemed like she had a burden lifted off her shoulders after talking to Sage, so I'm glad she opened up. Now we just wait to see exactly what they discussed in future episodes.
She's plus three now, so looks like we're gonna have to help her out and bring it back to plus two soon
It's plausible, because it just came out of the blue. He wanted a valid reason for Maya to have needed the free tuition, and he might've had a separate idea for it at the early stages of the game. However, he might've shot it down and came up with something else, which is the loan.
It could also have been prepared since the early stages of preparation, however he didn't put much thought into it and considered it a plot device just to add to Maya's drama and didn't really do much research into it, instead just basing it off what little knowledge he had regarding student loans. If that was the case, he definitely didn't consider it to be an important aspect of the game, thus it'll probably be resolved in the next 1 or 2 episodes. I hope it is, because I don't want this loan thing to haunt Maya for the rest for the game when we could have character development and just not give a shit about fucking student loans.
MC on the preps' porch is a scene you get when you signal the DIKs, innit? I've seen it a good number of times, so can't really get onboard with this 'gay MC' thing.