Wow, what a beauty! I love the pink/blue combo!

Have you asked the seller where they got it from?

Congrats on getting her!

Interesting topic!
I would assume they where not in bags in the slumber party box.
  It seems on Pink Dreams that the bag is not sealed, but taped, which could indicate that it has once been one of those UK clearense bags that has lost the card and then been  taped. (where the bag itself  on those are not sealed, just sealed with the cardboard attached to it). Also the thickness on the bag seems as sturdy as on the clear bags, much thicker then the bags usually made for mail orders. However, the text on the bag is not the same as on the clearence ponies with cardboards, so I would assume it is not one of those. Neither does it look like the one on Taffeetas page that was included with the kitchen.
But, it DO remind me of the bags from the giftpack extras in the US. The only one I know about is the Scrub-A-Dub-Tub Giftpack (oh, holy grail of mine!), but as rare as those seem to be, there could be versions that we are not yet familiar with. That, or as mentioned above, as a mail in offer from something.

Scroll down on here to see the SADT-giftpack. Its hard to see, but doesnt the bags from at least Spring Song looks like the one for Pink Dreams?
https://mylittleponyaccessories.weebly.com/small-sets-rock-a-bye---sweet-dreams-crib.html

was she sold to you as a greek variant?

1. What got you into collecting MLP?
I loved MLP as a child, and had several of them. I'm not sure what got me into collecting as an adult, but I guess nostalgia. get the ones I wanted as a kid, and then I just discovered more and more. 

2. Did you like MLP as a child?
Yes, loved them! My favourite toys!

3. What generations do you collect?
Mainly G1, as I'm an 80s child. But I do collect some G3 ponies, and have ponies from every generations present in my collection.

4. Who is your favorite pony?
Tough question, there are so many pretty ones to choose from But Cherry Treats is one of them. The perfect balance of white and streking red, and just a hint of green in the symbols. I also have a soft spot for Medley, and of course Lemon Drop,  which I collect variants of.

5. Who was your first pony?
Im not sure it was the first pony I got, but it is the first pony I remember I got, so I would say Wedding Bells Confetti.

6. Who was the last pony you got?
German baby Lemon Drop complete with backcard and accessories

7. What is your favorite generation?
G1

8. What is your favorite piece of media? (Any of the shows, comics, back cards, etc)
I'm a MOC collector, so I love the backcards of the ponies. Also a lot of merchandise ^^

9. What is your favorite pose?
I dont really have one for G1, but for G3 it is Sunny Daze pose.

10. Do you own any customs / have you made one?
Yes, I have a few, both original characters and babies for existing ponies. I think I have made two myself, but I think I will leave that kind of work to those more talented

11. Who is your biggest pony? Smallest?
Biggest? Hmm. I dont own anything especially big, so probably any of the Plush ponies. Or G3 Styling ponies.
Smallest? Petits or charms I guess.  Want to get the worlds smalles ponies though.

12. How many ponies do you have in your collection?
Geez. Last time I counted was over 10 years ago, and at that point it was over 300. Since then, everything has been in boxes, although I still buy.

13. How is your collection displayed?
Most is in boxes unfortunately, but I have a few (recent purchases) on my bookshelf by my desk. But we are building a ponyroom (very slow progress though) so I hope I soon will be able to display properly. 

14. What is your least favorite pose?
Not really a fan of Tootsies or Shadys pose. Nor BBEs but I dont think they count as a pose.

15. What is your dream collection like?
Uhm.. My collections is very non focused, as there are so many things to focus on, that I want. MOC, Merchandise, complete with accessories, nirvana, so I'm not sure what my dream collection is. 

16. What was your biggest pony purchase (in terms of how many items)?
Not sure. Maybe Paradise Estate, as that is a lot of different piesces  

17. What is your favorite part about collecting? That there is always something to collect, you will never have everything. And that after 30+ years, we are still discovering new things about the ponies. And of course, all the people I have get to know during the time

18. What is your favorite pony website?
My little wiki, Chrissytrees acessory site and the MLP Scrapbook is my main go to sites.

19. What flaw(s) can you not stand?
I'm not superpicky, but cut hair and restorations I avoid. I want as original as possible. And of course big flaws like markers and stuff.

20. How complete is your collection?
Not anything near complete, at all, and probably never will be either  too many wonderfull things out there that I still need 

Leikin is a navy blue sea pony with blue and yellow hair, a ribbon theme, and wears barrettes.

Kinda fitting, as I'm from Sweden, and our Flag is blue and yellow

Oh, I had no idea that Moondancer had two toned tail as well. Then I need to get her I got the red tailed Sparkler, but was nervous when ordering as I knew they where replacing her.  I wish they would had made these kind of differences on all the ponies.

Funny thing, I chose between Trickles and FLutterbye, as they where my childhood ponies and both those where the only ones without votes before I  voted. No I feel bad for poor Trickles

I prefer the second set, as they are more colourfull.