How would I persuade somebody to not get a tattoo?

Congratulations on finding someone you love and see as a lifetime mate. My guess is your girlfriend is young. Sometimes immaturity, certain medications (i.e. antidepressants), and not planning for the future can lead to decisions we latter regret in life. I wonder if she could see herself as a mother or grandmother with this large tattooed snake on her body? What is her motivation for such an extreme large tattoo? Would she consider having the design done in henna first to try out the idea? In the end it would be her decision to make. It may change how you feel about her or not. Good luck, hope there was some shred of wisdom you could find in this answer.