I agree. It's nearly impossible for her to be pregnant. However, missing periods for any reason can indicate a larger health problem, so she needs to get that looked at.
However, I think many of us on here are concerned that you don't seem to know how babies are made.
Your penis would have to be inside her vagina with no condom or other protection. That's it. You don't have to "cum", because you precum (that stuff that comes out when you're hard but haven't done anything?) contains sperm. That's all it takes, so please, if you do decide to have sex, use a condom from the very beginning.