| Quote #1
Elizabeth would go her own way; and never had she pursued it in more decided opposition to Lady Russell than in this selection of Mrs Clay; turning from the society of so deserving a sister, to bestow her affection and confidence on one who ought to have been nothing to her but the object of distant civility. (2.16)
It's odd that Elizabeth, otherwise so snobby, would be positively democratic in her choice of friend. Or perhaps she just likes having someone around who's so obviously inferior in her eyes that she can take advantage of her without complaint.
| Quote #2
Anne Elliot, so young; known to so few, to be snatched off by a stranger without alliance or fortune; or rather sunk by him into a state of most wearing, anxious, youth-killing dependence! It must not be, if by any fair interference of friendship, any representations from one who had almost a mother's love, and mother's rights, it would be prevented. (4.3)
Sir Walter's objection on family grounds doesn't sway Anne, but Lady Russell's attitude as a friend does persuade her, since Anne does believe that Lady Russell has her best interests at heart.
| Quote #3
"But you, yourself, brought Mrs Harville, her sister, her cousin, and three children, round from Portsmouth to Plymouth. Where was this superfine, extraordinary sort of gallantry of yours then?"
Among the navy men, friendship is so strong that they'll do things for their friends they wouldn't even do for themselves. Compare also Captain Harville having Benwick's miniature, originally intended for his sister, reset for his new bride-to-be – even though it's painful, he would never say no to a friend.