Bad idea
Loaning money to friends is a bad idea.
Loaning money to girls you are sleeping with a worse idea.
Loaning money to girls you are dating is the worst idea.
If they are a good enough friend, hot enough in bed, or a good enough girlfriend, give them the money - if they are really in need and you can afford it.
Every single loan will f---k up a friendship or relationship.
I have a weakness for hot pu--y. I am currently owed at least $3000 by 4 or 5 chicks. My choice has always come down to - get the money back or keep the friend.... I've always chosen the friend, but I still look down on them for borrowing and not paying..
Good luck.
-Sean