Yeah, even though I've completed Nar Shadaa and Dantooine, she still won't give the topic to select a class. Is it that she only gives you those when you have full dark/light side points or is it something else?

You need to be minimum level 15 and strongly to the light/dark side.

If your playing neutral, you wont get this option. You must have an alignment of at least I think 80-100 or 0-20 for that option to open up.