Domestic to International Gatwick South

We are headed to Barbados in three weeks for Christmas and will be connecting with interlined luggage from a domestic flight with Aer Lingus. My 80 year old mother (who is pretty fit but not so good at walking longer distances) is coming with us so I was wondering if any experts out there could give me some idea of the process and distance of getting from an Aer Lingus gate to the V-Room. She is not too proud to use special assistance although I would probably send the rest of the family ahead so they can enjoy the facilities for the short time available.
Thanks in anticipation
Thanks in anticipation