When do I (25M) tell my girlfriend (25F) that I am not okay with her getting a booty lift?

My girlfriend and I have been together for 10 months. She's great and we have a good time together, everything is going great. Except that...We were at my parents place for a family get-together this weekend and she spent a lot of time talking to my sister (28F) and my mom (50sF). I came home this afternoon to find her crying because she hates her body and wants to get a Brazilian Butt Lift. I'm not sure where we go from here.<br><br>I absolutely do not want her to get a Brazilian Butt Lift. I really like her the way she is now and she looks very nice. I also think that cosmetic/plastic surgery is way too dangerous and I do not want her taking that risk. I really don't want to tell her this, but I feel like I need to tell her now or never because she might go ahead with it if I don't tell her.<br><br>&#x200B;<br><br>TLDR: Girlfriend is thinking of getting a BBL, I absolutely do not want her to get one. When do I tell her this?