If she's remarkably strong, I'll CONSIDER skipping her for a little while and coming back later. I'm not to her yet (just beat Erika), but I do not want anyone to die.
Same goes for Koga, whom I hear can be very bad. I should be able to get by him just so long as I remember to take Antidote xBajillion into the fight, though.
Blaine would be trivial, and Giovanni's main issue will be making sure my Pokemon can outspeed his in order to cause Fissure to fail. Should be easy.

( Other thoughts, and commentary on current status - next post will come when I have the time to write the text, as it will likely contain a good deal of chatting. [Or perhaps that's the next post... anyway, lot of talking either way.] )