you are right about that, author could have skipped on some details for just moving the plot in that direction, but it doens't change that she still didn't get special powers, we can guess that the mana rain Shadow used on her boosted her skills a bit other than making she recover.
Ah right, the "curse", is possible that after Cid removed the negative effects of the cursed blood she got a natural buff from it, we know the villain is good in a fight but if he fought her when she wasn't expecting a battle and was suffering is not a surpirse that she lost.
I don't rememeber every detail of the novel, is even possible that stuff got changed.
She being able to arrive to the VIP area is pushing but can be expained from a total recovery + buff, she was one of the top fighters around after all, the chaos in the arena for all the people around and she knowing what places had no guards for a secret infiltration.
And we don't know if she sneaked in, she was ready for death, maybe she killed every guard when running and got there before any alarm.