Luna is getting cheeky with Moon.

Well... she has a point there about being immortals

Moony give her a break, she's desperate.

and at least she's got a point.

hmmm my "the Nightmare moon will get pissed and make woona cry" is tingling.....lets just hope that;s not happening! please ~ XD
but this is truly a good story so far

Hrrm, actually, an ultimatum might actually work here, if the actual concern is that Luna should have more friends: "Look, it's not healthy to rely entirely on one pony. Please, go make at least one other friend. As long as you've got at least one other friend you do things with regularly, I don't mind being your friend as well. But if you don't, I don't want to see you; You should be too busy making more friends to spend time with me."
The actual wording needs work, of course; I'm a socially clumsy nerd, I can't be trusted with such delicate subjects.
But I could definitively see a strong-willed, yet kind-hearted, friend forcing their less social friend to make other friends with such an ultimatum.
Of course, the danger is for the friend to give up entirely and be friendless - it would be even harder to convince her once she's lost her strength.

Thus why immortality isn't all its cracked up to be XDDD

yeah it be either a blessing or a curse

That also means she could end up hating you eternally Luna. Don't push her that far...