I sent a naughty pic of my gf to another girl
Is this something that would worry you if you were her?
I found it funny even she thinks so, but I will apologize.
Even if she finds it funny, it is right to apologize to the person you sent the naughty picture to. Any unsolicited pictures like this may be a form of sexual harassment and you should think twice about doing so in the future.
I sent it to my friend, not to my gf. This is something I wouldn't do, she is right and I'm sorry.
I am delighted that you find what was wrong with what you did and I hope you strive that you don't do it anymore in the future. I would recommend you delete any explicit photos you may have on your phone as it can also be weaponized against you in the future.