First off, thanks for all the replies they've been very helpful.
I think I may have been a bit vague in my original post, fingers crossed she's not been diagnosed with diabetes yet. This was just a prelimary test because she'd been sick and was drinking a lot, so the gp thought it best to do a b/g which came out at 6.8, and as she hadn't eaten for about 3hrs, this seemed towards the upper end of normal. The next step is a urinalysis and a tolerance test if abnormal, so I can only wait on those results.
I may just be worrying unduly, but I thought I'd post on here to get some advice