It's nice when someone can see the error of their ways and make a correction. Many people can't even get to the first step of that let alone the second step. The person who got this tattoo definitely owned up to their mistake. They got a tattoo that wasn't grammatically correct and they noticed it. Although I applaud their attempt at fixing it, I think they should have just left this one alone.
If I was reading this tattoo and noticed the missing 'N' I'd just let it go. The tattoo is about God, after all. Judge not lest ye be judged, right? There's got to be some grammatical God-rule where you don't have to say "an" before talking about him. That's not how this woman felt since she decided to pop the N in there for perfect grammar, bad tattoo.