Facebook? Ads or posting links in Groups? MySpace? How/Where? Boards? Which ones? Social News Sites? - Which ones? Blogs? Other Ideas?
If however, your application has a different target demographic and you simply wish to test the waters with this group then sites such as TMZ (and other gossip related rags) is your best bet, IMHO.
Here is the rundown of what she said: -Doesn't read online news/blogs -Clicked 5 or so Facebook adds lifetime -Watches a copious amount of online TV (Hulu etc.) -When looking for new services online she googles what she is looking for (budget manager, etc.)
If I was going to go about a marketing plan based just on this anecdotal evidence I'd say SEO is quite important, and perhaps getting some adds during online videos (how expensive is this?) would be good because she seemed very adverse to clicking on anything she didn't go looking for in the first place.
If your app has a very broad market there's no point going after every 18-25/female because you can't afford to advertise to the whole demographic without some really really REALLY serious money. You'll need to "pierce the zeitgeist" with something that captures imaginations to get the word out.
Pierce the zeitgeist? I do sound like a wanker, but you would probably need to step up from typical "viral" marketing techniques. Don't go herding sheep with LEDs, step it up. How? No idea!