Getting your wife comfy on her road bike... hm... I guess you need to discuss with her what's at issue. If it's "twitchy" well, road bikes tend to be that way. She'll get used to it. My son is currently complaining about the same exact thing. He finds that riding on the hoods gives him the best feeling of control.

Use whatever pedals she's comfy with - no issues with that.

As for braking down descents, that will change when she's comfortable on the bike and confident of her route. Sounds like she needs to do GMR with you on May 5.