
Lori's suggestion of contacting one of the Irish Rescues seems to be a brilliant suggestion to me. A donation to their rescue would, I imagine, be most useful and they are experienced with dogs travelling by ferry - your mum may also be able to travel in their transport with them thus only being separated from her dog just for the ferry crossing.
It is something I would definitely investigate further - beneficial to both parties it would seem :)
Wiccaweys is another rescue that regularly brings dogs over from Ireland.