When you posted this question, I'm betting that you weren't thinking "gee, I sure hope I get a lecture instead of an answer". Right?
And so... to answer your question: Unless they are in a patchy area, battery has died or have their settings to "airplane" mode, chances are you have been blocked.
I don't suggest this, but if you really want to know 100%, here's how you do it. Before calling, add *67 to her phone number. It will show up as a "blocked number" or "unknown caller." All I know is that I wish that iphone would allow us to block these, but they don't. I don't know of anyone that answers these type of calls (I sure don't). Anyway... if it rings, you can likely conclude that your number has been blocked.