Many women get hyper sensitive and can not take direct stimulation for a few minutes after orgasming.
Its possible she had an orgasm...
The way to be sure is to look at her chest and throat... if she her skin is flushed on her chest or throat, then she had an orgasm.
The clit will first get firm and be easy to keep track of... but as she nears orgasm it will become very soft and very hard to keep track of...
Keep your stimulation going... and gradually increase its pitch and/or pressure, or narrow the area of stimulation... or some combination thereof.
What often happens is that guys keep the exact same thing going on... and not realizing that when you know its near you need to crescendo....
After she gets all sensitive... try seriously lightening your technique and licking over a larger less focused area and allow her a 'refractory' period of a minute or three of very gentle stimulation, NOT directly on the button...
Chances are she will pull your head back up to the action station when she is ready to build to another orgasm.