There are a significant differens regarding Mr Collins attentions to Lizzy. In P&P2 we see Mr Collins going after her and singeling her out from her sisters as soon as he decided that she would do when Jane was "taken". It is difficult not to pick up his attentions.

In the novel Lizzy realized that he had chosen her to be the mistress of Hunsford Parsonage, first after his application for the first two dances at Netherfield. We have suspected, since the letter, and known of it, since his talk with Mrs Bennet, but Lizzy is kept unaware until this moment.
But I liked the ringthrowing scene in P&P2 better than Mrs Bennets stirring the fire, as we can "see his thoughts" when he consider the girls, and when he makes his decision the rings sound like a bell announcing that this is the right choice.