Athletic, normal weight, pre-diabetic result

I got a physical last week for the first time since high school. I didn't even think about the possibility of anything besides good/normal results. But, I've got an A1c of 5.7 (not to mention a "bad cholesterol" LDL of 113!). So needless to say I'm surprised. Diabetes definitely runs in my family, but the people with it are older, overweight, and sedentary so I've never considered it to be a real risk. Obviously I was misguided. I'm 30, female, extremely active (weight lifting 3 days, HIIT cardio 2 days, vigorous yoga 4-5 days per week, plus I live in NYC and walk a lot) and have a generally healthy diet (not insane healthy, I live in NY not LA) with lots of protein, healthy fats, and brown carbs. I'm 5'9" 140 lbs. I'm right on the margin with 5.7. Part of me feels like I may be doomed by genetics, but I am absolutely going to try my best to lower it, if there's any possibility. I cant see exercising any more than already do - so I've gotta go to diet. I generally stay under 200 grams of carbs per day (I know this isn't low carb), sometimes more if I'm going out to eat with friends, etc so I could go lower but my question is how much? Does it depend on how your body is responding to the particular foods you're eating? The amount of information out there seems overwhelming (cut carbs / keep carbs but only certain ones / timing them / something about a meter?) and it's largely geared towards people who have a lot of weight to lose and need to be more active/significantly cut calories. So I'm looking for a bit of clarity. Anyone have experience with being in the non-overweight/sedentary group with pre-diabetic reading? How do you manage? Thanks