It sounds like you're trying to keep the conversation alive rather than take it somewhere. You have no destination for the conversation, and thus no point for it. This runs the risk of the talk just petering out and her losing interest, like what's happening now. Always, always ALWAYS have a reason for messaging her (obviously this doesn't need to be as strict once you've met, kissed, fucked and maybe dated her). When on the website, it's usually to get her number (or set up a date, if it seems possible). When texting her, it's usually to get her to meet up.
Online game guide:
http://forum.casanovacrew.com/viewtopic ... de#p107370
Guide for text messaging (but many rules are applicable to online game too):
http://forum.casanovacrew.com/viewtopic ... 44&t=17951