H1B and H4 at the same time?

Hello,unfortunately there were problems with my wife’s green card procedure (wrong advice from our lawyer, so the wrong category was filed). Therefore, the application has to be withdrawn by us and we have to start again. That is a long story.For this reason, her H1B now has to be extended. Because her previous H1B has expired, she must do the consular processing. This means, she has to do her interview in the consulate in Frankfurt/Germany. I’ve had an H4 so far, but this one ended with my wife’s H1B. I would like to extend my H4 too. That’s not hard, I did that the first time without a lawyer. The difference: at that time my wife already owned her H1B (Aproval Notice and Interview).My question: Can I already apply for an H4 if my wife only has the approval notice for her H1B but has not had another interview yet?Due to my question: My wife has to travel for her interview from the US to Germany. There are nearly 200 miles to Frankfurt, so it would be sensible if we both interviews on the same day.