Tried to jump my nieces battery on a 1997 accord but hooked it up backwards. Now there is zero power. We replaced the battery and still nothing. Boneheaded move but it is what it is. Any ideas on what could of happened. Or what likely got fried?

 

Most likely one or two of the main fuses got burnt out.
Check engine bay fuse box.
Probably a big one with two fuses in it. (100, 70) or (80, 50) Not sure.
That would be the first thing to check.
May need some tools in order to get the fuses out.

Let me know how it goes.