Why does Miss Havisham send for Pip?

The two reasons why Miss Havisham wanted Pip to come to Satis House are:

1. In Ch.7 we read that Miss Havisham is alone and is bored and would like to be entertained, so as a means of relief for her boredom she asks Pumblechook, her tenant, to send a small boy to her house who would entertain her and relieve her boredom. Pumblechook informs Mrs. Joe who in turn sends Pip to Miss Havisham's house:

`And couldn't she [Miss Havisham] ask Uncle Pumblechook if he knew of a boy to go and play there? Isn't it just barely possible that Uncle Pumblechook may be a tenant of hers, and that he may sometimes -- we won't say quarterly or half-yearly, for that would be requiring too much of you -- but sometimes -- go there to pay his rent? And couldn't she then ask Uncle Pumblechook if he knew of a boy to go and play there? And couldn't Uncle Pumblechook, being always considerate and thoughtful for us -- though you may not think it, Joseph,' in a tone of the deepest reproach, as if he were the most callous of nephews, `then mention this boy[Pip], standing Prancing here'

`She [Miss Havisham] wants this boy [Pip] to go and play there.

2. In Ch.44 Pip is able to compel Miss Havisham to confess that she used Pip as a means to torment her avaricious and selfish relations namely, Sarah Pocket, Miss Georgiana, and Mistress Camilla:

I was liberally paid for my old attendance here,' I said, to soothe her, `in being apprenticed, and I have asked these questions only for my own information. What follows has another (and I hope more disinterested) purpose. In humouring my mistake, Miss Havisham, you punished -- practised on -- perhaps you will supply whatever term expresses your intention, without offence -- your self-seeking relations?'

`I did. Why, they would have it so! So would you.