Don't respect the frog unless it is set up during oki. Nu's dash is fast enough where you can just dash right past the frog while activating it and it will completely whiff. You can also dash into the frog to activate it and then IAD back to avoid the electricity and be in a position to stop Rachel's approach. Or try to throw her. Even if she techs, the frog disappears.
And frog summon is easy to punish. Frog summon is 49 frames, which is more than enough time to D her. The air summon can be stuffed with 6D/2D easily in most cases as well.
As for getting out of the corner, you have CA and burst. OD > sword super is also decent since it's plus on block but it burns a lot of resources. If you wanna frustrate the Rachel player, you could try barrier and instant barrier at random times to mess up their blockstring timings since Rachel is execution heavy. If they are just auto-piloting their blockstrings, proper barrier blocking might leave a hole open for you to escape from.