Miss Havisham’s influence on Pip is great. From a young age, she brings him into her home and subjects him to Estella. She uses him as a trial run for Estella, to teach her how to get a boy to fall in love with her. Pip’s view of class and love is distorted from these interactions.
Since Pip is the narrator, we would not know what was whispered into Estella’s ear. However, Miss Havisham whispers into Pip’s ear often. The most common whispers are related to Estella’s beauty.
“Miss Havisham would often ask me in a whisper, or when we were alone, “Does she grow prettier and prettier, Pip?” And when I said Yes (for indeed she did), would seem to enjoy it greedily.” (pg. 66-67 of the enotes etext, in chapter 12)
It is in Miss Havisham’s best interest to make Pip fall in love with Estella, so she can grow up to break hearts and be Miss Havisham’s revenge on the male species. It works, because Pip does fall in love.