You sound like you skipped through the entire game, otherwise you'd know who she is and what there is to forgive (or not).
I didn't skip anything, what would be the point since no one is here for the world-class animations, its all about the story so yes I know the vague generalities of who she is in relation to the orphanage but that doesn't really go any way to explain who she actually is to the MC, why has she taken such an interest since apparently there are loads of magic users who awaken and no one cares since Aya explained that 90% die within the first year.
For example why does she ask if he can fly yet as if its expected? Is it just a magic thing or is it related to his lineage, is he supposed to have wings too?
It doesn't explain to us exactly what the ramifications of what she did are, is it a minor thing? if so then why does she feel so bad about it?
If its something more major then how about explain to us what it really means?
Without knowing the details, consequences and alternatives then how can we decide to forgive or not?
That basically means you're left to look at the stat/flag changes in the code [or via a walkthrough] the see what that choice actually means/does and if there is a good reason to pick one over the other or if its just more of a flavour choice.
For example, when you pick who to side with early on [humans/non-humans] that is clearly a major choice but then later when you're buying a mirror you get a choice to try to convince the woman or just mention Tamara and so far as I can tell it doesn't really matter what you pick because it eventually just ends up being that you mention Tamara any way to get the mirror.
So in this situation I'm saying we, as the reader, don't have enough context to make an informed decision about Maria, it'd be nice to go more in-depth about what she actually did, what its done to the MC so far, what it means for the future and so-on.