NewType Voice 2011-07
Interview with Aoi Yuuki and Amy
Summary translation of how Amy relates to Madoka:
In the opening for Mahou Shoujo Madoka Magica, there was a black cat, and all the fans were saying, "That's Amy, isn't it!?"
So the staff said, "Okay, we'll call the cat Amy."
Then in the Drama CD included in DVD 1, the black cat was named 'Amy,' and her CV was Shintani Ryoko (who also played the role of Hitomi).