She starts developing an interest in Bingley.
A young man with money but no obvious talent, whose relatives are extremely manipulative and crass. They hang around and on Bingley who seems absolutely content to keep paying for their rather extravagant lifestyles.
Bingley best friend is a really stuckup jerk and he seems to rule Bingley's life (this is hypothetical remember). Bingley thinks the world of this fella.
If you felt that Bingley was far too pliable and thus unreliable, would you encourage Jane? Or would you point out the risks involved?
How could she trust his attentions when just a word from one of the others might have him running off to London never to be heard of again?