The Ragin Pagan's board-to-board with LeeUnit92
From Halopedia, the Halo wiki
It's not really speculation because it doesn't really matter, just like her alleged faith. To assume that Lopez is a Roman Catholic (or even that the specific faith has survived that long) because of a chance reference is also speculation, and yet that has stayed. The reference to The Art of War is doing no harm, and isn't offensive in any way.
Well it just seems like speculation. I mean the author could have had that in mind but to me it seems more of a religious thing since she constantly refers to her soldiers as rosary beads in the story.
Personally, I would much prefer a reference to The Art of War on a public site than a religious reference. Personal preferences aside, I don't see how having the connection to The Art of War does any harm, so why not leave it?
I saw it as more of her just being a motherly (and Catholic) person. And considering the vast amounts of warfare advice in The Art of War lots of things in the Halo Universe can be applied to certain passages. For example ONI's plan to capture a Prophet is similar to a passage stating defeating an enemy without doing battle (I don't remember the exact line).
Why would it be a stretch to associate Lopez with the segment of The Art of War? Lopez was the first thing I thought of upon hearing that passage.