There are a lot of lies swarming around the internet, a lot of them even debunked by Rowling herself, and Luna in particular was a character surrounded by lies. A very popular one stating that Luna was Snape's daughter (which Rowling already denied and that Xenophilius was really her dad). Naming Lilly after Lupin would mean that all Marauders would have made into the Harry's children's names (with of course the notable exception of Peter Pettigrew for obvious reason), but still all resource material I looked in do state that Lilly Luna was really named after Lilly Potter-Evans and Luna Scamander-Lovegood. (Luna eventually wed Rolf Scamander... Grandson of Newt Scamander, yes the guy we see in Fantastic Beasts).