Paxboy,
Your questions aren’t questions, they are statements, however, reading between the lines -
Yes, your friend should check their luggage right through to LHR so they won’t see it in VIE.
Yes, your friend can leave the airport rather than remainin transit, however it will be at their own peril, and they will have to remember to allow time to go through security when they get to VIE, so they can’t buy any duty free booze and some larger bottles of perfume.