and when Lydia's elopement with Wickahm becomes known ,Elizabeth realises the full impact her sisters behaviour is likely to have on their lives, as Mr Darcy makes his excuses and leaves her at the inn at Lambton:

Be that as it may, she saw him go with regret; and in this early example of what Lydia's infamy must produce, found additional anguish as she reflected on that wretched business.

Chapter 46

I find Mr Bennet's resposnse to Elizabeth, when she broaches the subject with him,quite annoying for he does realie,even in jest, that shoud Lydia disgrace herself at Brighton there would be serious ramifications for her ( and the family):

"Do not make yourself uneasy, my love. Wherever you and Jane are known you must be respected and valued; and you will not appear to less advantage for having a couple of -- or I may say, three very silly sisters. We shall have no peace at Longbourn if Lydia does not go to Brighton. Let her go, then. Colonel Forster is a sensible man, and will keep her out of any real mischief; and she is luckily too poor to be an object of prey to anybody. At Brighton she will be of less importance even as a common flirt than she has been here. The officers will find women better worth their notice. Let us hope, therefore, that her being there may teach her her own insignificance. At any rate, she cannot grow many degrees worse, without authorizing us to lock her up for the rest of her life."