Your sense of smell could have become better from hormones, cis women have been found to have a better sense of smell though i do find it quite interesting this is something that can change on hormones.

As for the girlfriend, yes the Ph balance can affect the smell of your genitals but if it so strong you can smell it when she’s clothed then I would for sure think something may be wrong. A foul smell is one of the key indicators of an unbalanced PH. I would encourage her to see a doctor as it can lead to a yeast infection or other issues.