Be Mine!

The bag can be bought from the vendor for 2 love tokens. It has 10 charges and its possible to get the same candy more than once so good luck!

If you've been wondering, you cannot complete this by getting the Candies through the mailbox or trade, you have to create the Candy yourself, making this the "hardest" of the achievements required for Fool for Love.

Statistically, you will need an average of 1+8/7+4/3+8/5+2+8/3+4+8 ~= 22 charges of Candy, meaning 3 bags, to create all 8 of them at least once.
(As usual keep in mind that it's easy to be unlucky and need much more than that, just as you might be super lucky and get all with 8 uses.)

The 8 [spell=70577] messages required for the Be Mine! achievement are received randomly from [item=21813], which has 10 charges and therefore provides 10 chances to get the required 8 [spell=70577]. Due to the random nature of getting [spell=70577] from the [item=21813], it will probably require several bags to complete the achievement. You can purchase the bags from the [npc=42172] vendor in any major city for [item=49927] x2.

You can collect a [item=49927]s by trading in one Lovely Charm Bracelet at the [npc=37674] vendor. The Lovely Charm Bracelet is created by turning in [item=49655] x10. You can get [item=49655] by killing mobs appropriate to your level while you have a [item=49661] in your inventory, which you also receive by talking to the [npc=37674].

Notably, this is the only path to get [item=49927]s that is not constrained by dailies; the faster you get your [item=49655]s, the faster you can accumulate your Lovely Charm Bracelets and the your [item=49927]s to buy the specialty holiday items and finish the Be Mine! and other [achievement=1707] achievements.

The best place to use your [item=49661] to collect your [item=49655]s is in [zone=5004]. Leave the zone set to normal mode to speed the process and reduce any damage taken.

After killing the first two bosses, go back to the entrance and head up the left corridor towards [npc=42172]. In the hallway there, kill the [npc=40923] mobs that continuously spawn. They can be AoE killed quickly (only about 3k health!), even solo, by almost any class, and each one that dies has a chance to leave a [item=49655]. You will have to kill the [npc=40925] mobs in the front and middle of the hallway first to clear room to kill the [npc=40925]s. However, be careful not to kill the two [npc=40925] that are standing at the end of the hallway before [npc=42172]; once those die, the [npc=40923]s stop spawning.

Depending on how quickly your class can AoE farm here, you can easily pick up 500+ [item=49655]s per hour; some classes report farming almost 1,000/hour. You will likely need a group to help you kill the first two bosses, though.

(Note: Technically, you only have to kill the first boss, [npc=40586], and activate the control panel, to open up [npc=42172]'s hallway to access the [npc=40923]s. However, the spawn of the 2nd boss [npc=40765] blocks your path back to the teleporter, so realistically he will have to be killed as well.)