Estella reports to Pip exactly how they feel, she says the Pockets
beset Miss Havisham with reports and insinuations to your disadvantage. They watch you, misrepresent you, write letters about you (anonymously sometimes) and you are the torment and occupation of their lives.
These people are obsessed with Pip and seeing him fail. Perhaps this has to do with Herbert (the pale young gentleman) not having success at Havisham's. Estella hauntingly assures Pip that Havisham doesn't find their information valid.
In this chapter, we find out that Miss Havisham's relatives hate Pip. We find this out from things that Estella says to Pip right toward the beginning of the chapter.
She tells Pip that the relatives all lie to Miss Havisham about Pip. They write letters to her (sometimes withou even signing them) saying bad things about Pip. She says that it would be impossible for Pip to imagine how much the relatives hate him.
They presumably hate him because they think he will get Miss Havisham's money after she dies.