Is 375cc too small for someone who is petite?

Thank you for the question.  
Generally speaking, the best online advice I can give to ladies who are considering breast augmentation surgery (regarding breast implant size/profile selection) is:
1. Concentrate on choosing your plastic surgeon carefully.  Concentrate on appropriate training, certification, and the ability of the plastic surgeon to achieve the results you are looking for. Ask to see lots of examples of his/her work. Sometimes, it is necessary to seek several consultations before you feel comfort will about your choice.
2. Have a full discussion and communication regarding your desired goals  with your plastic surgeon. This communication will be critical in determining  breast implant size/type/profile will most likely help achieve your goals. 
In my practice, the use of photographs of “goal” pictures (and breasts that are too big or too small) is very helpful. I have found that the use of words such as  “natural” or "C or D cup”  etc means different things to different people and therefore prove unhelpful.
 Also, as you know, cup size varies depending on him who makes the bra; therefore, discussing desired cup  size may also be inaccurate. Again, best not to discuss your goals and/or judge the outcome of the procedure performed based on achieving a specific cup size.
 
3.  Once you feel you have communicated your goals clearly,  allow your plastic surgeon to use his/her years of experience/judgment to choose the breast implant size/profile that will best meet your goals.  Again, in my practice, this decision is usually made during surgery. I generally select appropriate breast implant size/profile after the use of temporary intraoperative sizers and viewing the patient's chest in the upright and supine positions.
I hope this, and the attached link (dedicated to breast augmentation for petite patients) helps. Best wishes.

Its not the cup size or size of the implant that matters, its the look you're going for thats important. Those other two things vary and are not standardized for each patient. A 375 ml implant will be large on one patient and conservative on another.In your case, this will not be a small augment by anyones standards. Too big of an implant can cause long term issues that will necessitate further surgical interventions in the future. You can always wear a push up bra to get even more out of the augment as well. If you go too big, theres not much you can do. The wide medium range of choices is very versatile putting you in control of the situation. Cup size will depend on where you buy your bra
from as they are all different and there is absolutely no standard. I
try to get patients to disregard cup sizes altogether, and as they try
implants on go for what "fits" them. The size, character, and proportion
they had in mind, and whatever cup size it turns out to be will be the
right one.