Elvira tells TMZ ... "I didn’t get a heads up that Kylie was doing the costume, but she did the costume justice and it was very flattering." While it sounds like Elvira was digging the shout-out, she goes on to say an actual digital name-drop would've been appreciated.

She adds, "It would have been even more flattering if she tagged me."

Kylie threw up at least 4 different Instagram posts showing off her costume -- which was recreated to match Elvira's iconic look to a T. You can tell she respects the one and only, but as Elvira mentions ... Kylie never really connected the virtual dots for a notification.

She did tag the studio that shot these, and even gave herself a nickname ... "kyvira." Kylie got a lot of love in the comments, but it doesn't appear that Elvira herself said anything. It's also unclear if she officially "liked" any of Kylie's posts.