Yes, the use of "BBG" can be flirty.
The acronym BBG, which often stands for "baby girl" or "beautiful baby girl" in American slang, is often used in a flirtatious manner. As indicated by the reference material, it is a term that can carry a flirtatious connotation.
Therefore, when someone uses "BBG" to refer to another person, it can often be interpreted as flirting.
