It's a slightly odd comment, galaxy, but I wouldn't worry about it too much.
My dd is also quite bright when it comes to reading (she's older than your dd - nearly 8 and in Year 3 - and has the reading age of a 12-year-old or something). The ORT books (is that what your dd is on atm - the Biff, Chip and Kipper ones?) go up to about Level 16, so your dd is not about to run out of them any time soon. The ones dd was reading till recently were just like normal chapter books (about 100 pages long) and - you may be pleased to know! - did not feature Biff, Chip and Kipper! The only difference between them and any other book that dd might have picked from the library was that they had clearly been 'graded' for difficulty.
My dd has been taken off these books just recently and allowed to be a 'free reader'. This was partly at my instigation as I did feel that some of the subject matter wasn't 'age-appropriate' (there was one about child slavery and one about a boy whose mum runs off and abandons the family and he discovers that his dad isn't the man his mum has been married to, etc etc etc). However, there are plenty of age-appropriate books out there... My dd also started with the Rainbow Fairies (and dd2, who's in Year 1, is currently enjoying the Magic Pony and Magic Kitten series too). But she has progressed onto a whole range of books. I steer her away from the 'real life' 'issues-based' books (Jacqueline Wilson, et al.) and steer her towards fantasy-type books. She currently loves Cornelia Funke, and generally anything involving dragons, mermaids or other magical creatures. Between the Rainbow Fairies and now, though, she read a lot of Dick King-Smith and Roald Dahl and... well... there are loads of threads on here about good reading books for children of your dd's age. IMO reading which is age-appropriate in terms of content doesn't have to be ridiculously easy, and it's only because schools are so wedded to their bloody reading schemes that they see this as a problem. Think of all the wonderful 'children's classics' (Laura Ingolls Wilder, EE Nesbit, CS Lewis, Noel Streatfield, etc.)!
In my experience, it's not at all hard to supplement the reading material supplied by school, so I really wouldn't worry about this. It may be harder if the school are not pushing her in maths (not sure about this, as my dd is fairly average in maths), but I am sure that there are also possibilities there for supplementing her school work at home if necessary.
Hope this is reassuring. Sorry it's so long (subject close to my heart ).