Then I don't think it's worth it to still be skeptical over whether your gf can accept your stuttering or not. If your stuttering appeared around 6 y.o then it's very likely that your stuttering is a developmental one which is led by the genes unless back then you got neurological traumas, diseases, or the side effects of random drugs and if not then it's just led by genes. You can also assure it by asking your relatives/families about if any of them also have stuttering(i.e ask, don't observe bc stuttering can disappear at random ages simultaneously or he/she is just a potiential stutterer, namely he/she has yet to be triggered to stutter). If he/she also stutters the answer is pretty self-explanatory.