Companion tix rules?
 

My mother and her partner bought 2 companion F-tix from LON to OZ and back. While my mother still travels for business then her partner is more of a leisure traveller and due to poor health does not plan to make the return part of the trip. Now, what happens if one of the 2 pax does not turn up at the airport? Will my mother be able to check in alone and fly to LON or will she be denied boarding as it is a companion tix?