I don't know My sister Jodie but my 9 and 7yos read JW. Some of the books aged at younger readers, around 8 I'd guess, include Double Trouble, Glubbslyme, Lizzie Zipmouth, Video Rose, Cliffhanger, and the Werepuppy (that might be for younger children even). These don't deal with Teen Issues, more primary school age issues.
In addition to the titles Fennel mentioned you could also try The Lottie Project. Do not in any circumstances get the Girls in... books, DD2 (9) brought one of them home from school recently and thoroughly enjoyed the descriptions of teen drunkenness, snogging, going too far with boyfriends etc before I realised what she was reading.
DD fell in love with JQ about a year ago. She is a peculiar child who, sometimes models her behaviour on what she is reading about. DH kindly bought her a JW book (The illustrated mum) which was miles too old for her. When I spoke to other mum's at the school, they all agreed that JW's books always have issues in them. Divorce, bereavement, abuse etc. We have avoided them ever since and asked the library not to issue them to her. Luckily for us, the local bookshop has a limited number of english language books.