Did she pull back so hard becouse of his hands? Maby they had the calloses of a swordsman?...

I thought maybe she can sense a power in him.. perhaps magic?

I also thought it's because of the calluses of swordsmanship. Perhaps he's pretending to be incompetent so as to not get attacked by people who support the crown prince.

I this so too. Since she was an soldier in her last life she would recegnise that. As well as the fact that the "fool who turns out genious" second or third prince trope is wery popular.

That could also be the case...