Hola Amigos
I think it is a good idea that people can read here about the experiences that guitarists have of teachers and I hope that it can include teachers of any aspect of flamenco.
As for the first flamenco guitar teacher to appear I could not possibly comment!!!
But I am sure there must be many others and would hope to read about them here.
May I recommend the flamenco dance teacher Antoñita Ramos. I accompanied her flamenco dance classes in Cartagena at the academy of Margarita Amante and was always completely impressed.
Her technique is so clean and precise and this she teaches very carefully to her dance students. But also her whole feeling of flamenco is wonderful and I feel that the dance students also get that from her even if they are not sure how that is transmitted.
I always thought that Antoñita was easily good enough to tour and perform but she did not seem to be interested. This is a pity as I would have a job for her!

Saludos cordiales

Tomás