Just my professional and personal opinion:
She can use a human glucometer, but they are not calibrated for animals. So, in order to get an accurate reading, she should, ideally, have a blood glucose (BG) curve done at the hospital on a machine that IS calibrated for animals and do a test with the glucometer she chooses at the same time for comparison.
One of my cats is diabetic, and I am VERY distrustful of glucometers for animals, as a general rule. I find them to be off by 70 points or more on the in hospital studies I have done (especially in the high and low values, which, in my opinion, are the really dangerous ones). The only glucometer that I am aware of (there may be others, however) that is calibrated for animals is called Alpha Trak (I got mine on Amazon.com). It was about $175 for the kit, and it comes with 50 test strips and instructions, etc. The first BG curve I did on my cat was done with both the Alpha Trak and the in house lab machine. That way I could at least see what the difference in numbers were for myself. I have never been able, nor have I ever heard recommended, to take one blodd sugar value at one time on one day and be able to adjust insulin levels that way. Too many factors can affect a single reading, and it is, in my opinion, far more important to see a trend in a given day than to spot check values here and there and then not know where they go from there (some can be plotted as a bell curve, some are up and down multiple times through the day).
Diabetes is a life changing disease for animals and their owners. I don't think I truly understood that until my own cat was diagnosed. I understand the frustration and I really hope that things get worked out for your friend.