Cookie-cutter is a tool or knife used to cut cookies into special shapes, before the cookies are baked, such as cookies in the shape of stars, 4-leaf clovers, etc. A spin-off refers to a TV show that is based on a character who once appeared on another TV show. I agree with Nick's definition of cookie-cutter spin-off but I don't agree with how your friend used the term. Just because two TV shows are alike, does not mean it's a spin off. Actually, most TV shows that are spin-off are radically different from the show the character was originally on.

"Cookie-cutter" means something is generic or unoriginal or mass-produced. Therefore, if a TV show is described as a "cookie-cutter spinoff" then she is saying it is essentially the same as all other crime dramas; there is nothing new or exciting or different about it. I hope that helps.