It sounds like you're suggesting that since one teacher is encouraging two girls to program that therefore everyone in every girl's life is just as encouraging to them as they are to the boys.
Is that true for anyone? If someone I really respect is encouraging me, that's very persuasive but there are so many forces at work when choosing a career, I don't think there's any way to quantify that decision. But of course teachers make a big difference, for better or worse. This particular teacher, I know one of his female students is a successful 3D graphics engineer, another classmate works at Intel, etc.