You really don't need any other herb than Pueraria Mirifica. It's been eaten as a vegetable in Northern Thailand for generations without ill effects, arguably healthy effects, for generations, and it estrogenic properties are recognised in many clinical research papers.
Search this forum and google scholar. Herbal breast enlargement using other herbs, unless you have a lot of time, dedication, and the money to spend, is almost impossible... that's why many TG boards out there consider it to be a scam.
Bryony