brightlotusmoon | Female cat behavior

A surprisingly tender moment between Luna and Rose became something intriguing.
Since we brought Rose home back in June, Luna has been a bit standoffish and uncaring. Occasionally, in recent months, Luna would groom and nuzzle Rose, but those moments would be brief. Earlier tonight, I watched Luna walk up to Rose, sit down in front of her in the same meatloaf pose, and begin to lick and groom Rose's neck. After a few seconds, Rose began nibbling Luna's ear, but it didn't seem like a friendly gesture. I accidentally made a loud noise and the cats broke apart. Moments later, Luna shuffled closer and nudged Rose in a full headbutt to the shoulder. Rose put her ears back and batted Luna away, and the two briefly batted at each other, then ran off in different directions.
Later, I picked Rose up and held her out to Luna. They sniffed and touched noses. Luna licked Rose's forehead once. Nothing else happened. Rose stayed still for a moment, then squirmed and I let her go.
I am starting to wonder if Luna is finally accepting Rose completely and trying to develop a relationship, but perhaps Rose is wary because she remembers Luna's rebuffs in the past. If this is so, I wonder if Rose will grow out of her caution soon, because I can see this turning into a delightfully sweet friendship.

Thoughts and advice would be appreciated.