Have you ever contracted your girlfriend's unknown yeast infections?
Not through oral sex, no. But through normal sex, my partner and I often pass thrush infections backwards and forwards until we realise that one of us has it and both get treated. Sadly, it's just a potential consequence of having lots of sex as the pH balance gets knocked off and things can happen. If one partner has thrush, you should both take a treatment tablet as it's often passed back and forth during sex. Once you've had it once, it can make you more prone to it again and again.