Hmm.. I don't think you should no matter how you feel about her, Unless you know her in real life then only if you're ready for it :/

There are a number of things to take into consideration:

a) Are you comfortable showing your penis?
b) Do you actually want to show your penis?
c) Do you trust this girl enough so that she wouldn't pass this picture around?

A lot to take into consideration. If she really wants to see your penis, why not just show her it in a private setting with no photography involved. Seems to make a lot more sense.

NO

so many people get into trouble with pictures- even if she doesn't intentionally share it, someone could find it and spread it around, she could get in trouble (especially since you're so young) and it's just a generally bad idea.

that may not be a girl your chatting to on the web, it may have a s/n like "lilprincess13" but the real deal may be a 50 yr old starker or child molester. the internet is fun, yet still dangerous.

for a joke (i didnt recommend this) find some porn star's penis and send that to her...
but dont listen to me

just trying to help..