I recommend a pre-emptive strike...
Be honest and tell them how good their daughter is at giving head, describing her technique in detail, and then ask your girlfriend's parents if they think she picked it up from her Mum.
After being honest about that, I don't think you'll have to worry too much about the occupation issue.
See honesty is best...
I tell people who enquire that I create multimedia and design websites, mostly educational and entertainment material. Which ones? You probably have never heard of them, they're not on TV or anything - so how about the Final 4?.
See how it works?
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