Well, Reimu apparently escapes anything he can do to her by leaving reality? Then what about going to other realities instead of just leaving reality altogether? Yukari can flee into her gaps, accessing this sort of "void" between them; it's fleshy and full of eyes, and sort of seems like a pocket dimension. Not to mention immersion. From Reimu's case, leaving the reality the battle takes place in will escape the Universal+ range of Shulk's hax. And if the area the gaps lead to is actually a void and not a pocket dimension, then it's sort of like leaving reality in a similar way that Reimu does.
And the point about toying with opponents, don't make this a repeat of Yukari vs Bill Cipher. There it was ruled out that Bill is more sadistic and more likely to toy around, allowing Yukari to cut to the chase more easily, taking the win. But this is much different due to Shulk's precog and definitely not messing around as a result. On top of that, Yukari's limited precog won't work on him. But there's a catch. In the SBA, there's no prep, and opponents that lack precog will simply know that they have some opponent to take down, and they won't be phased by being teleported to the battlefield. Yukari knows she has to defeat somebody, but, she should probably be surprised by how her precog suddenly isn't working on this anomaly that is Shulk. Knowing that she'll get in the fight and not much else without her precog, this should be foreboding to her. In that case, she's far less likely to toy around, only being able assume that if the opponent resists her precog, they must be pretty dangerous. How does she infer all of this just from the fact that she lacks precog towards her opponent? She's extraordinarily genius. Just look at the intelligence on her profile and I don't need to explain much. If she can solve a 1000 variable math equation instantly, not to mention thousands of years in age building her wisdom, then in this foreboding situation where precog doesn't work, her wisest first choice should be to flee into a gap, where I've already worked out that Shulk might not reach her in. Even if he tries to chase her into the gap before she closes it, this is speed equal starting at 4 kilometers, so he probably can't.
Now the real question is, if he can't hax her when she hides in a gap, can she do the same? I don't know of Yukari has ever been shown to boundary manip people when she's inside the gap, but one thing's for certain, she can at least open up smaller gaps that fire danmaku at the opponent while she's hiding. But the bullets likely won't work against Shulk's precog and other abilities. If this is the case, I'll accept incon. Unless we consider stamina. This is always overlooked in threads that end up with incon. Shulk can run for days, managing a high stamina, but Yukari is superhuman or even limitless, so the danmaku isn't stopping anytime soon. One question I have to ask, if Shulk's stamina is completely spent, will he be completely unable to fight anymore from extreme exhaustion? Yukari can outlast the several days this battle might last in order to pull this off.
And about calling Shulk your precious, I guess I should apologize, but just keep in mind this wiki is usually toxic, and in heated debates, you're likely to get jabs at yourself and the character you're defending.