im mad that she has tattoo!
Well, you probably should be concerned a little. It may depend on how long ago she got it, and how she feels about it now. Tattoos do reveal a dark-side to a person. I have two, and I absolutely despise them - I was 17yrs old when I got them, several decades ago. No one should deface God's creation, and permanently marking one's body is exactly that.
So yes, Holy999, be concerned! But, like myself, she may even share your sentiment? Talk to her gently about it, and she where she stands on the issue. If she's not phased by it, and you still are, it's time for a serious reassessment...