If you play on legendary, you should know what happend so there are no spoiler for you.
Some general advice:
This level is one ot the easier parts of the game.
For the little fights - don't block just keep rolling pressing B.
If you roll with pressing B you do not have the problem, that you get hurt when two enemies try to hit you at the same time.
Boudica fight:
Part 1 :
Block her whole attacks, than hit her with X,X and Y
Sometimes she would avoid if you press X,X,X so keep X,X,Y for some little extra dmg.
This part shouldn't this hard.
Part 2 :
Like i said, keep rolling pressing B.
On legendary you don't see the heavy attacks and sometimes she will put her swords in the ground for some Dmg.
If you press B for every swinging swordattack, you avoid all the dmg.
After that you can hit her with one or two swordhits pressing X
If you want to vote this down, please tell me why so i can change these things.
Sorry for my english - its not my native language.