Assuming your daughter hasn't been diagnosed then if these are fasting figures, there is every chance that she is diabetic. However, you shouldn't try to diagnose diabetes through finger pricks - so given your family history and concern go to your GP and ask for a Glucose Tolerance Test ASAP.
If she is already diagnosed then it might be a good idea to discuss treatment options with your your GP and/or diabetes specialist. Assuming that these are fasting figures, they aren't terrible but they could be better.
If she isn't diabetic and these aren't fasting figures then don't worry. Non-diabetics can easily get these sort of levels (or even higher) after a big meal - they should just drop back quickly. If you are interested then test immediately before a meal and then every 30 minutes afterwards and plot a curve - the difference between a diabetic and a non-diabetic should then be quite obvious. Other than insulin and the various drugs used to treat diabetes there are no magic products that lower blood glucose (well, alcohol does but there can be err... side effects, and it is probably not a good idea for your 13 year old daughter!). A good diet and regular exercise is by far the best approach.
It is possible that she isn't diabetic yet, but still has slightly raised blood sugars. This could be the so-called pre-diabetes condition, and your GP should be able to tell if this is the case. If she has pre-diabetes then good diet and exercise can often stave it off for years, or even prevent it from manifesting as full-blown diabetes at all.