As long as you drink less than 3 cups of coffee per day, there is no relation between coffee and breast size.
This myth about coffee and breast size spread due to a study which indicated that 3+ cups of coffee a day was associated with smaller breast sizes, but this study is surrounded with lots of criticisms like in the way of calculating the breast size. There are no other evidences or research done to back this claim.
Conclusion - You can enjoy at least 3 cups of joe with no risks of shrinking breast sizes.
