How to deal with oxalates

A close relative had pretty bad kidney stones. She was told to drink lemon juice daily and to add calcium to her diet. However in doing a deep dive, it became apparent, that calcium affects oxalates quite considerable, and oxalates affect osteoporosis quite considerably. (and scoliosis of the spine). So now my relative has an oxalate reading that is off the charts. yet no doctor can advise where is the egg and where is the chicken here. Has anyone had an oxalates reading of over 700 and what did they do? Be nice to know because there does not seem to be much of any medical advice