Can see both points of view... Have a friend who spent a fortune on having her teeth sorted out - straightened etc and I at the time questioned the cost and pain for not alot of gain, her teeth weren't bad at all. But I realised it was the confidence she gained from it, much more smiling and being happier with herself.
Having said that I'm not saying go for it here, teeth are different to what is in effect surgery with all the possible nasty outcomes and I presume she gets the idea of the risks and that you love her tits as they are (many others would too I bet lol) At the end of the day as the others have said it's her decision, let her know you love her tits as they are but if she goes with it she'll get your support to get to the final result.
C-cup doesn't sound too bad, the only proviso I would have in your position if she was to go ahead was to say they have to look natural, you don't want her nipples pointing to the stars when she's standing up!
