lol Simna, I kid. Anyways, you did use that PK fire thing that no sane Ness player would use, and it messed Nana up a few times. But remember, no sane Ness player doesn't use it not without good reason! I remember that whenever you missed or any insane Ness player missed, he or she was either grabbed, wavesmashed, or punished in some other excruciating manner.
Unfortunately when it does land Nana becomes more ******** than usual and racks up damage. Fortunately however, Popo is only as ******** as the IC player. Simple hopping and firing an iceblock will either cause Ness to dodge, absorb, or get hit by it. All of the following which lead to Nana escaping, after taking 20% or so.
PK Fire also collides with ice blocks, which is kinda lame cause ice block spamming doesn't work too well. The worst part is the flame stays there and nullifies any other ice blocks that are Nessbound.
Downwards DI? Anyways, seems like you got 2 options: go towards Ness or away from him. I guess if you DI away you could frantically try and air dodge, roll, or wavedash away. None of which really seem to promising. DI'ing towards Ness and going for the shieldgrab seems like the better idea to me. Granted that most the time if the Ness manages to land a PK Fire, they'll usually just follow it up with a foward smash. Seems like an easy moment to WD outta shield and punish Ness, but at the same time seems kinda risky because he'll probably be able to land the f-smash first. On the other hand it's better than DI'ing away and getting creamed while DI'ing the wrong way :-/ Hmm... guess I didn't know as much as a though about this...
In conclusion don't worry about it, cause there aren't any Nesses dumb enough to use it, and very few that are smart enough to use it effectively.
. And Simna doesn't like Nana. Unless of course you count char-broiled Nanaburgers. Nanaburgers are how Simna relaxes before his next match. 