Well OP says that it doesn't happen very often so even though she's 29, she may not be a regular drinker which means she isn't really sure what amount gets her hammered. They could be drinking different types of alcohol with higher or lower percentages which can be confusing. I just feel like everyone in these subs always talks smack about the other person and I feel like sometimes they need to be represented as well. Although yes, you are right in the sense that OP's gf should probably just stop drinking all together if this happens every time but maybe they ARE regular drinkers and it happens only once every 20 times they drink or something?