green tea inhibits 5 alpha reductase, which is important for the metabolism of steroids into testosterone and estrogen, so it depends on your body whether it is good for breast growth or not. I was born a male, so inhibiting the production of testosterone is good for me, but inhibiting 5 alpha reductase will have an effect on those born as women inhibiting some estrogen synthesis, but it is probably not a big deal in normal doses

but remember green tea is natrually high in flouride, so if you make green tea with flouridated water you could end up with a condition called flourosis