Asymmetries abound, as you have noted, Milena. But, as we discussed last week, let's back up and ask what our intentions are. With any challenge, illness, condition, etc., what is it you want to do? Your student describes a “dodgy tailbone,. I would like to understand more about what she means: is it painful, dysfunctional, ???. And, then - what is causing it. She said she has been diagnosed with unequal leg lengths. Well, most people have one leg longer and one leg shorter; but this doesn't automatically mean it is dysfunctional, any more than having a bulging disc or torn meniscus means that you will have pain or disability. One way to diagnose a shorter leg is by looking at the pelvis and seeing if it is “crooked,, however, the research I cite in Your Body, Your Yoga shows that many times what is observed is not a crooked pelvis, or rotated sacrum, or shorter leg; it is actually just one side of the pelvis being longer than the other. The leg may be fine, the sacrum neutral, but one ilia is longer than the other.
In any case, your student has already said that the orthotics affected her negatively, so if one “map, isn't working, how about trying a different map? Not being able to walk or run because of an orthotic tells me - she needs to get rid of the orthotic! If she was fully functional before her toe surgery, then I can't imagine her asymmetry is really a problem.
Again, neither you nor I are doctors, so we can't diagnose her or offer medical advice. But, you can explain the “flying your own plane, principle and encourage her to find a way to fly her own plane without pain or problems. She may have to 1) find a new doctor, and/or 2) experiment a little and see what happens. For example, what happens if she spends a week without the orthotic? (If she has been wearing it for a long time, it may take her time to adjust to not having it.) Doctors are there for her benefit, so she is totally within her rights to find one that is actually helping her and she doesn't have to accept being “off kilter, or not being able to run again.