mey-rin

Height: 165 cm (5'5")
The glasses-wearing maid of the Phantomhive household, Mey-Rin is enthusiastic about her job but is extremely bad at it, primarily due to being clumsy. She often adds too much soap while washing clothes, trips and shatters the good china, and generally causes chaos due to her clumsiness. When tasked with important duties, she stutters and panics, exacerbating her natural clumsiness. Her glasses, which do little to improve her coordination, were the first thing Ciel bought for her, and she refuses to replace them for sentimental reasons. It's implied that she has a crush on Sebastian, as she becomes even more clumsy when he is watching. Despite her awkwardness, Mey-Rin is actually quite pretty, though this is hidden by her glasses and maid outfit.

In episode 21 of the anime, it was revealed that Mey-Rin was previously an assassin before Sebastian took her in as a maid for the Phantomhive household. She used to be a sniper who didn't use a scope, thanks to her sharp far-sighted vision caused by her ill-fitting glasses. Physically fit, she can handle a sniper rifle like a handgun and keeps hundreds of rounds loaded to minimize reload time. This background was also confirmed in chapter 33 of the manga.
(Source: Wikipedia)
Her name written in Romaji is Meirin.