Flushing forces cannabis to use up any remaining nutrients left in the plant, none should remain to effect the taste or smoke of the buds.
However, if done to early, it can leave your plant unhealthy, so timing is key.
I would not advise flushing if you still have not feed her yet, mainly because you will strip the nutrients out of the soil.
When you decided to flush, make sure you ph the water to about 6.5 for soil.
I am currently growing DWC, but I flush my bucket every other solution change and it definitely increase the growth rate, by stripping all the old nutrients away from the roots. Here is an image of 4-1 gallons jugs. The two dark ones are the solution change, and the two lighter one is what I get with a 2 gallon flush for 30 minutes of so.
Hope this helps.
I know DWC and soil are not the same, but it was the best current example I have.