Hi there, welcome to PsychCentral (PC).

I would try to think of what your family has to say as you will what I have to say :-) It's just their opinions based on their life experiences. They cannot make you feel guilty if you are wholly comfortable with what it is you want to do.

Is there some reason you want to get this done right now, instead of waiting a few years? There is no hurry and there's a lot of life ahead of you probably and this particular decision will alter your history in ways you may not have imagined or understand yet; having/nursing children will be different and the men you meet from now on out, how they feel about your breasts might be important to you but not something you can easily change after this event.

I had 34B breasts when I was your age and gained a great deal of weight and much bigger breasts. One's breasts can increase with bearing children too, as well as in the natural course of living one's life. Were I you (but with my life experiences/hindsight), I would wait until I marry and ask my husband to give them to me/pay for them if he wanted them too :-)