Mira is an extremely intelligent fighter. She would start off by analyzing Tanjiros fighting style and search for anything to exploit.
standard tanjiro tactic lol.
altho i don't know how good she is, tanjiro can analyze and connect multiple data points to connect the dots and conlude akaza's vague ability by picking on subtle clues and fragmented information from his memories to figure it out and unlock a way to deal with it.
that's his best showing as far as i remember, he does demonstrate outstanding analysis abilities in the fight against the emotion clones and kyogai but it wasn't on that level, alternatively he can also spontaniously modify his forms to create to deal with whatever oppoenent he is fighting.
granted i forgot where specifically, but he is capable of doing that.
Her borrowed power primarily works as a massive stat amp allowing her to one shot people she couldn't even scratch before and to keep up with people that appear to be teleporting even to those far superior to herself
"appear to be teleporting" is quite vague terminology, and while you do a good job providing descriptions it's not really giving me any quantitative indicators to go by.
and while the one shot attacks is quite deadly if it lands, the STW's perception amp is relative to the user's speed level, so if she is far slower than he is she is that many times slower in his perception.
When Mira does find an opening she will usually try to pull off some unconventional move, which gives it really good element of surprise
Tanjiro in this key has the selfless state, a state that cuts off all the senses and turns the mind invisible, making him entirely detached from his own physical existence essentially erasing all It erases the extraneous thought and emotions completely, to the point where he registers to the ability to sense emotion and intent on the level of a plant and become a part of the background, so "confusing" or "unconventional moves" won't really have any effect as he is operating purely on instinct, closing off any unnecessary thoughts and only picking the most necessary moves which he will perform as if he is blinking, hence why "intent" disappears in this state.
The characters at this level also have a danger sens like ability that allow them to predict attacks with zero data input at all to warn them of it, dodging it before it happens, adding that to his future smell and surprise attacks like what you've shown won't really work on him.
this is assuming she even survives the decapitation, because from what i could see the RE takes time and doesn't happen instantly, and she is not surviving that long with an opponent so much faster than she is anyways.
