The first time the reader appears to be told is in #8 when she turns human so she can do the nasty with Hardball. He then says he "saw ALL of her" in issue 3 when she switches to human mode, although in issue 3 you do not see the missing legs. Even in #8 it's not easy to tell. I didn't notice until I looked that the pants she's wearing are now deflated. The characters never actually say "Wow, no legs!"