I think you will be trolled here because of your thread, We have a general sense here that before asking questions. One should use his/her skills in looking for the knowledge and acquiring it, and by doing that we ensure the complete elimination of noobs and people with unbelievably stupid questions.
Anyway back to the topic, there are two methods to make your file undetectable by the AV, first one is to use an encryption software. Check these two links
1 and
2 and read carefully. Now I can't be sure that the two programs provided are safe to use, so you are on your own. The second method is hexing your malware, and that means using a hex program to minapulate you malware structure to make it undetectable by and AV, of course without corrupting the file as well. Check this link for more information on this subject
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How to infect your victim(in this case your GF)?
The answer to this question depends on you and your persuasion skills, you could send it by email or through skype.
I don't know why am helping you?
