Even a cheap meter should give consistent results with other meters. It's pretty easy to get your meter calibrated incorrectly, so I'd recalibrate *both* meters. If your mom's meter is right, you're still getting spikes. And well, if your meter is right, those are scary spikes. That's part of why most diabetics trust their A1C numbers more than their daily numbers.
Even if you turn out not to have diabetes, the book Triskeliongirl is suggesting is good. Our endocrine systems are complicated, and a tiny change in the function of one part can have very large effects. So yes, if your thyroid doesn't work right, it can affect your pancreas, and your ovaries, and your pituitary gland... Thankfully most of us are old enough that the pituitary gland is off :).
Note: Even with the meter error, you may *still* be looking at impaired blood sugar regulation. The high spikes you're getting are a lot higher than the high spikes my sister, dad, brother and I would get when we acted as Mom's normal guinea pigs while she was learning to use her meter. A "spike" on us would be around 110 (even for sugary stuff), and most random tests would have us in the 90-110 range. Mom uses any handy normal person as a quick way to check meter calibration after all that testing.

