Ruby/Horsethief may be appropriate. I know my wife wouldn't have wanted to go boating at all while she was pregnant, out of an abundance of caution, but Ruby probably isn't as risky as riding in a car, except for the remoteness. It's permitted for overnight, but if you can go mid-week, you can get permits for this week.
Maybe even stay in town, and float from F St. to Vallie Bridge? There are a few rapids, like Badger Ck and Tin Cup, but she could walk those I suppose. It's been too long since I floated that section to remember if it might be too rough, but it would be borderline. Sure is closer than Ruby, though.