It could be that she was picked on about her breasts, maybe she watched T. V. and u know how they protray a unrealistic body image that's makes girls & women feel they have to live up too. It could be she just doesn't like that part of her body.
The best thing for you do is just compliment her & tell her that overall u think she beautiful & that she's beautiful regardless of her boobs size. Girls love compliments, makes them feel better & more secure, especifically from their boyfriend or husband, it's helps. :)
Oh shit this is a real problem. Have a serious talk with her and try to tell her that you like her no matter how big her boobies are. Get close to her and comfort her the best you can cause if she continues doing this then she'll be hurting herself more.
1. The majority prefer bigger breasts. Comments like "I don't mind small breasts" and "you have ass to make up for it ". This is not a compilment, just adding insult to injury. 2. The media potrays bigger breasts to more attractive and that those women are seen as more feminine. 3. Comments from men like "women with small breasts look like children or teenage boys". 4. Women with bigger breasts get more attention. 5. Men may have ignored her breasts completely in sex. 6. She may have been teased for being "flat chested" during her school days.
Why? The answer is right in your question details. She's an A cup, and feeling bad about it because girls are constantly bombarded with the message that you need big boobs to be pretty or all guys only like C cups and above and all that.
Just tell her she's pretty and that you like her body. I used to be very insecure about my small breast but since I've started to buy myself some cute bras ( not even padded woohoo) I feel much better and more confident. You should buy her underwear :)
Society loves to push the perfect female body image of a female with large breasts. So her insecurity isn't all that uncommon. Flip through any girly mag at the grocery checkout and you'll note 90% of them have at least C's. But that being said yeah it really doesn't matter; at least not to me. If she's old enough the implant option is always there if it bothers her that much. My wife had it done and every day of my life she brags about how much she loves them. I'm impartial to them really; sure they're nice to look at but she looked fine before too. For me it was worth the $10k to have her stop whining.
I'd just do you best to re-assure her that she's beautiful no matter what and see if you can win.