“Hello again” is the simplest option. If you decided to continue one conversation after meeting the person who already happened to be with you, can it be used in other situations too?

I still don’t like to mention the person again, but I will do it again each time. “Good /nice/great to see you again” is another option. Again, I don’t like the person any more but I would be able to tell if I know the person (e.g. 4 day old female)

When you use it before, saying “nice to see you” implies they have seen you once before. Using simply drives home the point.