The “bad” news is I think colleges will likely not give her much “credit” for her school context when it comes to test scores, given her family context. It may affect things like how they evaluate, say, her number of college-level courses however.
But the “good” news is I think this just places her score in the “probably just doesn’t matter” category.
One other thought that may help–I think sometimes applicants think in terms of perfect candidates, and comparisons to such a candidate. Like a perfect candidate would score a 100, and the more imperfections you have, the farther from 100 your score gets, until it is too low for being admitted.
To the extent it ever works like this, it is really only at formulaic admissions colleges. In contrast, every AO for a selective holistic review college I have ever seen discuss this has basically rejected this view, or at least it is more complicated.
What might be true is you need to meet some basic standards for academic preparation. But since test optional people are being admitted, we know you don’t NEED a score for that.
There may also be some other basics–active in school, good character, that sort of thing.
But once they have that pool of kids who meet their basic standards, they change to looking for reasons to say yes. Like, what about you could really help contribute to our student body in a way we value. And there is no one perfect candidate, just lots of different kids who they end up wanting to admit for lots of different reasons.
OK, so I think from what you are describing, it is very, very unlikely that whether or not they consider her academically well-prepared will depend on submitting or not submitting.
Assuming she is deemed academically well-prepared, then it will become all about those other basics, and finally about in some way standing out as someone they want for some reason specific to her.
And that can be stressful since it is so unpredictable. But stressing about this test score doesn’t have to be part of that. She can make her best pitch for why this college should see her in particular as someone they should want, and then she has done her best.