Hello Loiner
It is truly awful the first time, but in the early stages, it comes and goes, so she may well recognise you next time.
When I'm with Jan, I reinforce who I am all the time, buy saying "it's Bruce" or "it's your fella". Does it get through? Maybe because sometimes, as well as she is able - and that is not much - I do hear something approximating to "Bruce".
Because I know Jan is in trouble knowing people [especially as she can no longer see], I always reflect that I know who she is. It is always important to reflect that the person is still the same person really, they have just had to change a bit to adapt to a body that is fighting them. We need to recognise them even if it is very hard to do so, help them, and be proud of them for they are fighting a hard fight.