It's common sense to not fall for situations like these.
You
DO NOT give money to anybody online unless you know them personally or its financial transaction.
You need to look at the situation and think about how if this person had her own business why would she need to be online looking for money or love.
You dont give money to anybody unsecure over the net nor do you give some woman you dont see money over the net.
What these people do is called online fraud and they use social engineering to mind melt you into feeling almost sorry for them to give them money.
You you get a pm from one of these people again use the security feedback on Yahoo! below to report them and send a carbon copy of their transcript with it.
security@yahoo-inc.com
Also read up on this page for some partial imformation on social engineering.
http://security.yahoo.com/online_interaction.html