Well, if you're trained as an EMT and you come across the scene of an illness or injury and decide to announce yourself as an EMT and step in then it would be a good thing to commit to your choice, commit to your patient, and commit to doing what you can to help the patient get to the next level of professional care.
My first impression of your choice to not go further on your patient assessment was "Weren't you curious?" You were trained to be curious and you could have scratched that itch without touching her or manipulating her. More in depth questions and observations were called for here, if for nothing else than you announced yourself as an EMT and me, as a responding paramedic, would expect a more thorough indication that you made an attempt.
If I get on to a scene and others tell me the guy with the patient told them he was an EMT, unless he stepped right up to the plate and gave me a professional response I would brush him aside. I would want him to act like an EMT and I wouldn't take the time to wait for him to show it or even produce ID! You communicate you are what you are by being what you are.
In the end what you did was appropriate; you showed up and protected an injured patient from others who could have been dangerous...even if no one on the scene was. You did no further harm. That's all good.
But I think you cheated yourself of a learning experience because you didn't take that extra step to practice your evaluations or to challenge yourself to figure out what was the BEST you could do to assist the patient under the circumstances.
Your description showed some notable hesitations and hesitation is something that you need to eliminate from your diet if you're going to get good at the game. Taking a moment to discern is much different than hesitating because of insecurity or because you had to figure if what you read in the books was right.
Also, don't forget the immensely important role you could have played by connecting with the patient and letting her know a little of what to expect when the ambulance gets here, while also checking with her to see she IS in a position of comfort and stability.
All this, of course is a matter of practiceuntilyougetitdown!