I've had some readings be very different from one another myself. One day after a meal my bs was 147, so I washed my hands (again) and tested on the other hand, it came back 128. Another time I tested 138 on my monitor, then tested again (same hand, same finger) on my mom's monitor (two different brands) and got a 187! I brought it up with my dietician and she said that the number is based off of what you get in that specific drop of blood at that specific time, and that bs can change from one minute to the next or be different on one side of your body vs. another. Overall bs monitors have something like a 10% variable one way or another and can be interpreted as being 10 to even 20 points in either direction. Just as I've found monitoring your BP can be a very inaccurate way to determine whether you have preeclampsia if you or the medical professional don't know what they're doing, bs monitors are pretty inaccurate too. Those with Type I diabetes have the option of having something installed under the skin of their hand that checks bs regularly throughout the day and removes many of the variables that can throw off readings on the little monitors we're using, and is usually paired with an insulin pump. But that's because they live with the condition their entire lives and could die if their bs begins to dip.
As far as the advice my dietician could give me, she said to consider it a bit like weighing yourself on the scale. You want to try and measure on the same monitor around the same time every day, to give yourself an idea of how you're doing rather than taking the numbers as gospel. Also mine came with a small bottle of solution that, if I ever suspect the monitor itself may be reading inaccurately, I can use the solution on a test strip to make sure the monitor doesn't need recalibrating.
neither of your numbers are high that seems so odd to me. Again crazy the differences between what doc's consider normal range. 
i always need alarm reminders lol
That nurse's comment seriously makes my blood boil 
women with normal or even low BMI's get GD all the time too. More than likely the reason you failed the testing was because you were tested late; from what I understand, most Dr's offices test between weeks 26 to 28, in an effort to discover the GD as soon as possible. A great many ladies pass the tests only to develop GD later on down the line, and because they've been deemed 'fine' nobody knows anything is happening until they give birth to very big babies. A close friend of mine just had this exact scenario happen to her, and gave birth to a perfectly healthy but HUGE 10lb 11oz boy. I'm of the opinion that if doctors really wanted to eliminate all possibility of anyone developing GD, they would just have every pregnant woman start testing her bs 4x a day starting at 26 weeks. Then nobody would have to drink any nasty drinks or be judged by ignorant nurses. 
