Okay okay okay the thing about spiro is, and I cannot stress this enough, and I'm not yelling at you or any of my trans siblings, but if there is one thing that gender affirming care practitioners need to get through their skulls its this:

THE EFFICACY OF SPIRONOLACTONE CANNOT BE DETERMINED VIA BLOOD TEST

Spiro works by changing how the body deals with testosterone by binding to the the receptors that would normally take it. Its still going to be floating around in the bloodstream but it wont be used for anything. Ideally, at least. The trouble with spiro is that you cant really test to see how much of that testosterone is actually binding with the receptors, so its difficult to quantify how well its working. Generally speaking, I have seen most gender affirming care clinics take an approach that is guided by patient satisfaction and I suspect that this is why. Things might actually be fine with her T levels.

What's happening with your girlfriend's (congrats btw, wishing you an happy first anniversary in advance) numbers happened with me and I'm pretty happy with my results, so take that for what its worth. I'm wondering if estrogen patches might help her safely get her numbers up. Oral estradiol has a pretty short half-life and can cause some pretty dramatic daily spikes whereas patches deliver a much more consistent level over time. If she decides to try those out I recommend the twice weekly patches since its less of an issue if you lose one/its easier to create backup stashes.