Rachel Shelley guest starring

Actress Rachel Shelley has announced in a column on DIVA magazine that she has filmed a guest spot on Once Upon A Time. Here’s the quote thanks to Rachel Shelley RX

My disappointment at missing the convention was muted somewhat because that same weekend I set sail on an immaculate tall ship through aquamarine waters in fairytale land [...] working on ABC’s hit TV series Once Upon A Time.

Thanks to the website’s Twitter account we know the dates during which she filmed, which put her guest spot squarely during the filming of episode 2.04 “The Crocodile”. Considering her allusion about “setting sail” it makes sense she filmed an Hook episode.
Her character is most likely Milha, “a woman who’s often at her village’s tavern and is bored with being a wife and mother. Yearning for adventure, she joins a band of thieves”. People have speculated that she could be Rumplestiltskin’s wife and Baelfire’s mother. We only need to wait for the official press release to confirm our suspicions!