Oh god, that sounds quite bad. Her teeth will hurt even more if she doesn't have them fixed :/
How about the other girls, how did you bring up the topic of going bigger?
When you think about it, breast implants is just another form of body modification. Lighter forms of body modification include makeup, hair dying, etc. Then a more medium form of body modification would be tattoos, ear piercings, etc. Breast implants is one of the more extreme forms of body modification since that requires surgery, leaves a scar, very expensive, etc.
I have always felt that asking a girl on a first date "are you interested in getting breast implants" is too direct. What I have always done is lead the conversation in that direction, and then pop the question. I would ask "do you have any tattoos". Regardless if I get a yes or no, I them move on to "have you ever gotten any plastic surgery", then finally "how about getting big boobs". From there I would get an honest answer from them and the question is not so abrupt. I have always gotten a "no" from them, but not because I am rude or asking in an awkward manner, it's just that breast implants were not for them. I suspect this is the case for ~95% of women.
One time I told a girl that I met online, not yet in person, that I am looking for a girl that wants to be an Instagram model. She said that she "avoids Instagram as much as possible". This tells me that she is not the type of person that wants attention. And let's be real about it, the fundamental reason why women get plastic surgery of any kind is for attention. They may say "I am doing it for myself", but on a subconscious level the reason why they are doing it is for the approval/attention of others, whether it be from men or other women. Very few women spend thousands of dollars and weeks of recovery on breast implants and never show them off. Almost all the time, they wear low cut clothing, going out, posting pictures of themselves online, etc. withing days or weeks of the surgery.