<human>: Me and my SO have been dating quite a while now, 3 years. We've had the usual bumps along the way but right now at a strange crossroads.

SO has recently taken to the idea of getting both her nipples tatoo'd.

Some back story is that, my SO is notoriously impulsive. She is far too impulsive, I am far too conservative (not politically). It works for us as a couple to help level each other out.

SO has gotten piercings before that she regretted. She has gotten tattoos she now regrets (they're not ugly and they aren't major regrets or anything). 

I am just NOT on board with this nipple tattoo idea. I cant tell you exactly why, but the permanence of it on such a sensitive body part weirds me out. And I love the pair of knockers shes got just the way they are. A tattoo is already risky enough for conservative ole me, but Nipple tattoos just feels completely ridiculous.

Her response is that "its MY body and I can do what I WANT!". And I understand that and always feel that way. But I also feel like that after dating for 3 years with plans to get engaged and married, dont I at least have some sort of say in something like this?

 If she wanted to get a really stupid tat on her ass, I would offer why I dont like the idea but ultimately let her do what she wants, because who gives a shit its an ass tat.

But a nipple tat? Seems way more... Personal? All that on top of the fact that I am 90% sure this is just an impulsive phase she is in that she wont care about later, and I'm nervous.

How do I go about this? Do I as her partner of 3 years have a say in what she does to her body, or am I waaaay off base in feeling that way?

Could you distill the essence of the text into 1-3 sentences?
<bot>: Girlfriend of 3 years wants to get nipples tattoo'd and I am against it. She is saying its her body and I shouldnt have a say really.