Since the -- -- shire were first quartered in Meryton, nothing but love, flirtation, and officers have been in her head. She has been doing everything in her power, by thinking and talking on the subject, to give greater -- what shall I call it? susceptibility to her feelings; which are naturally lively enough. And we all know that Wickham has every charm of person and address that can captivate a woman."

There is very clear path to this disaster. It has been building since the --shire arrived in Meryton.

Their visits to Mrs. Philips were now productive of the most interesting intelligence. Every day added something to their knowledge of the officers' names and connections. Their lodgings were not long a secret, and at length they began to know the officers themselves. Mr. Philips visited them all, and this opened to his nieces a source of felicity unknown before. They could talk of nothing but officers; and Mr. Bingley's large fortune, the mention of which gave animation to their mother, was worthless in their eyes when opposed to the regimentals of an ensign.. -- Chapter 7

Lydia's and Kitty's behavior chasing the officers becomes part of the local gossip, as Miss Bingley notes when she is teasing Darcy

if you can compass it, do cure the younger girls of running after the officers. . -- Chapter 11

They are still young enough to be temporarily distracted from the officers, but not for long.

Their eyes were immediately wandering up in the street in quest of the officers, and nothing less than a very smart bonnet indeed, or a really new muslin in a shop window, could recal them.. -- Chapter 15

Mr. Collins being nothing when compared to the officers is not surprising. However, L&K steadfastness to uniformed men is repeated.

With such rivals for the notice of the fair as Mr. Wickham and the officers, Mr. Collins seemed likely to sink into insignificance; to the young ladies he certainly was nothing. -- Chapter 16

Lydia spells out her ambitions to her sisters.

Have you seen any pleasant men? Have you had any flirting? I was in great hopes that one of you would have got a husband before you came back. Jane will be quite an old maid soon, I declare. She is almost three-and-twenty! Lord, how ashamed I should be of not being married before three-and-twenty! My aunt Philips wants you so to get husbands, you can't think. She says Lizzy had better have taken Mr. Collins; but I do not think there would have been any fun in it. Lord! how I should like to be married before any of you! and then I would chaperon you about to all the balls. -- Chapter 39

Lydia sees herself being the center of the officer's attention.

In Lydia's imagination, a visit to Brighton comprised every possibility of earthly happiness. She saw, with the creative eye of fancy, the streets of that gay bathing place covered with officers. She saw herself the object of attention to tens and to scores of them at present unknown. She saw all the glories of the camp -- its tents stretched forth in beauteous uniformity of lines, crowded with the young and the gay, and dazzling with scarlet; and, to complete the view, she saw herself seated beneath a tent, tenderly flirting with at least six officers at once. . -- Chapter 41

Lydia is revealing to Kitty her involvement with Wickham.

When Lydia went away, she promised to write very often and very minutely to her mother and Kitty; but her letters were always long expected, and always very short. Those to her mother contained little else than that they were just returned from the library, where such and such officers had attended them, and where she had seen such beautiful ornaments as made her quite wild; that she had a new gown, or a new parasol, which she would have described more fully, but was obliged to leave off in a violent hurry, as Mrs. Forster called her, and they were going to the camp; and from her correspondence with her sister, there was still less to be learnt -- for her letters to Kitty, though rather longer, were much too full of lines under the words to be made public. . -- Chapter 42

Sometimes one officer, sometimes another, had been her favourite, as their attentions raised them in her opinion. Her affections had been continually fluctuating, but never without an object. -- Chapter 46