Testing Early

So I want to test Saturday(12dpo) or Sunday(13dpo)! I know that is early but I have good reason. If I remember correctly if you have good reason then it is okay. My reason is that I gave my sister the link to my chart. She is stalking my chart like mad and analyzing everything. I told her we wouldn't test until at least 15dpo. I want to test early just in case I get a BFP. That way I can alter my chart so it looks as if I am out this month! But maybe I am just making excuses to test early...