There are unlikely to be tons of books in a school library at the 1200 lexile level that are going to be really interesting to a pre-teen. I'd write and let the teacher know that your DD is not finding interesting or enjoyable books at her required level, and ask the teacher for a list of suggested books and let the light dawn spontaneously about perhaps needing to explicitly change that instruction.

Until then, I'd look for collections of short stories so that the 20 minutes of reading at her lexile level actually gets her somewhere. Andrew Lang's collections of fairy stories might appeal, and "The Blue Fairy Book", at least, is at the "right" lexile level.