problem is even the best tattoo artist in the world can't stop the lines from fattening up a little in time. This is true with any tattoo.... But specificly when you are talking about the level of detail this would require... it is not going to be pretty!
I have a huge mermaid on the side of my leg, with fairly complicated larger scales. when it was first done the scales were very clean and crisp. Now after a short period of time, you can deffinately see a little softening of the the lines. These are BIG scales. what she is talking about would be small scales!