I think Elizabeth means pretty much what she says - that being Darcy's wife would create such happiness as to outweigh being censured, slighted and despised by everyone connected with him, and having her name never be mentioned by any of Darcy's family.

Against this, Elizabeth would place the attractions of being married to a man who is good-tempered and kind (by Mrs Reynolds' account), willing to change when convinced he is wrong, honourable, capable of witty and stimulating conversation, and with a very nice house. So she's willing to marry him even if Darcy's family refuses to recognise her.

I suspect Elizabeth may also be aware that Lady Catherine would interpret her comment as just referring to Darcy's wealth, but I don't think Elizabeth cares what Lady Catherine thinks.