If you want to be pro at reading IOS, start learning body language and micro expressions. Micro expressions are very quick movements of the mouth and eyes that communicate specific emotions. People can hide their feelings, but it's damn near impossible to hide micro expression, as they happen so quick and subconsciously.
On the most basic level you'll be able to pick up her mood and interest in the current situation. At an advanced level you'll be able to know (with near certainty) when she is lying and how she REALLY is feeling, emotionally, during conversations.
These are the same tactics police officers, FBI, etc, use to detect lies and it's also why poker players wear glasses to hide their eyes.
Pay enough attention, and practice. Eventually you'll pick up on it without even thinking about it. You'll be aware of someones true feelings towards you simply by "reading" them.
In some ways it's a curse, because you don't always want to know, but you can't help it.
Women are much better at lying than men, and it's harder to get a read on them, and there are a lot of reasons why that is.
Mostly it has to do with HOW they lie, but I won't go into it unless someone really wants to know.
