So, basically, if it requires more than a "yes" or "no," that makes it open ended?
An easy way to think of open-ended questions is to think of the first word that you start your question with. Any question that begins with the word 'what', 'why', or 'how' cannot be answered with 'yes' or 'no.' Questions that begin with 'should', 'will', 'have', etc., can be answered with a 'yes' or 'no' response and are called closed-ended questions. Closed-ended questions aren't always bad. They are sometimes a normal part of conversation, and aren't a problem if you know how to keep the conversation going after her very limited response. However, for the most part you want to stick with open-ended questions. You'll get her talking more, revealing more information, and this makes it easier to keep the conversation going.