Jaina had every single advantage in the book fighting Caedus.
He had already lost an arm, she started the duel by plunging her lightsaber through the stomach whilst cloaking to hide her presence.
He wasn't interested at all in their fight and she admits several times in the book he is ludicrously more powerful.
She had to use ambushes, distraction and hit and run on him to kill him and he still could've easily killed her.
I mean seriously he hooked his saber to his belt that is how much he didn't care about fighting her.
He had his wife and daughters death on his mind the entire time.
Not to even mention Luke was bostering Jaina and tricking Caedus.
May as well use Sheev getting thrown down a hole by Vader as a reason why Vader can beat him.