I'm with the thinking that "Magic To Make The Sanest Man Go Mad" (DSC) is its own isolated loop, and that it ultimately doesn't matter whether Gabrielle could "see into" it or not, because the outcome would be the same from her perspective either way.
There's only a need for her to intervene in a situation where Michael would die but for that intervention.
If Michael had been dead post-loop, then she could have come back and intervened, but since Michael wasn't dead when the loop was finally broken, there was no need.
I'll gently push back a little as to the "need" aspect. Gabrielle says in "Perpetual Infinity" (DSC) that she has seen Michael die
many times. She didn't necessarily attempt to intervene on her individual behalf in every one of them. And on the flip side, I don't think we should presume
too assuredly that her intervention was in fact truly
necessary to Michael's survival, even where it
did occur. For instance, in "Point Of Light" (TOS), Amanda says:
"Sarek and I always believed that Spock used logic to pinpoint your direction. He might have known what time you left, how fast you were walking, what direction you were going in..."
My impression was that she'd seen countless alternate histories but they all had the same ending, where Control destroys all life in the galaxy.
I thought that was just histories based on what she could change.
Absent clarification to the contrary, I find it an attractive idea that her inability to change the outcome may be directly reflective of each "ending" she witnessed being in various ways the inexorable result of her own intervention. By her very efforts to stop Control, she was actually unwittingly
helping it maneuver closer to its goal of bootstrapping itself. Now that she's been sidelined, the trick may be to get Control to fall into its own trap, to in some way engineer a scenario whereby its own efforts can be somehow turned around on itself, just as they did with Mudd in "Magic..."
It's rather like the "price" Pike must pay for taking the crystal from Boreth. She can change many things, but not the "anchor point" she keeps being drawn back to, the "prison" into which she is locked. (I do wonder what might have happened if she were to have "closed the loop" and eliminated
herself before she had the chance to use the suit in the first place? Food for thought...)
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MMoM