1. She's a master of disguise
The first part of being a master of disguise: you need the hair, makeup, and outfit to make you unrecognizable to the people around you. Does Emily have the money and ability to do this? Obviously. Part two of being a master of disguise: playing the part. Any actor will tell you that a costume will only take a person so far; the deceiver needs to really believe. After donning the hair and outfit, Emily has the uncanny ability to morph herself into any role her mission requires, be it a waitress, hospital clerk, or Hamptons socialite.
2. She has advanced skills in the art of hand-to-hand combat
It's a given that sometimes a spy will get themselves into a jam and the only way out is to kick some ass. Let's see, Emily traveled to a far off land, trained with a ninja-like sensei in the martial arts, and since her return has wiped the floor with multiple men twice her size. Need I say more?
3. She has her own personal 'Q'
Other than the women and martinis, what do you think about when James Bond comes to mind? The gadgets of course! Who is responsible for giving Bond these gadgets and providing technical support? Q, and Nolan is Emily's Q.
Nolan has done some very Q-like things for Emily. He has provided Emily with various cams for spying such as the shamu-cam and shell-cam, hacked computers and cell phones, and even created a computer program Carrion that had the ability to financially devastate Emily's archenemies. If Nolan isn't Emily's Q, I don't know who is.
4. She's always one step ahead of her enemies
A master spy can't be caught off guard so they need to be extra diligent about what potentially could happen and take the necessary steps to prevent any unplanned inconveniences. Did Mason's unforeseen investigation lead him to Emily's true identity? Yes it did. Was Emily one step ahead of him? You know she was.
Emily made sure he lost all credibility in the public eye, wound up in prison, and created a situation where he had no way of proving his innocence. Not exactly how she had originally planned, but Mason was taken care of.
5. She's a master at finding out secrets