Hi Claire
Your results are looking good, they have come down a lot so far. I'd suggest that if you can be around 4.9 or even up to 5.5 before a meal, then reducing some carbs should ensure you only spike by about 2 points, which will keep you under the target limit of 7.8.
15 sounds like it was probably your HbA1c, which is pretty high, but if you keep doing what you're doing, and reduce some carbs, it should be much better at your 3 month test.
In your OP you said your parents are telling you this is serious and others says it's just about changing your eating - well, they are both right, IMO. Exercise helps but reducing carbs is very important. You will also most probably find that it helps you lose some weight too.
I went from 22 stone to 12 stone in a year through low carbing, and if I can do it, anyone can