I think a lot of replies are here from women and women tend to reassure women that everything is fine in any given situation.
Triple A chest is basically no boob whatsoever. That in itself probably won't make you undateable. Most of us guys in the UK don't have a lot of choice when it comes to women, it's essentially a female market with way more guys wanting girls than girls wanting guys, mainly due to career women and overweight women. If your flat chested odds are your not overweight, so you'll likely beat them in the stakes so long as there isn't anything else wrong with you such as poor social ability or mental health problems, etc.
If you have a pretty/very pretty face a lot more men will negate the flat chest issue in their minds. I'm not going to lie to you, for many men it will be a negative but for only some it will be a show stopper in itself. However, many guys will still likely be able to get hard, likely far more so than if girl is overweight, hence why you'll beat most of them apart from the odd few guys that are into overweight women.
To my mind small breasts of say AA or A cup give the girl a pubescent look. This can be a turn on for many guys. However, there are many guys that like full on proper boobs usually B to DD cup. After that I would say are the real big boobs, E cup onwards, some guys are into them but some find them too much as in over the top and might give the girl a poor lopsided physical form look.
The main problem with AAA cup is that it doesn't look like there is any development there at all. Either the girl looks pre-pubescent, i.e a child or maybe even a masculine look. Personally I think 16 is too young for surgery and other options can be explored, i.e swimming, drinking milk, even going a little over on weight temporarily to see if that will kick start them off. Pregnancy can also boost their size but three are no guarantees with that and in general a partner is best to do that with. I would personally leave any idea of surgery to at least 18 if not older, probably 21 as rapid growth can suddenly set in. Till then I guess use padded bras, nothing over the top just to boast to an A cup perhaps to make it look like you've got something there.