Whats is the proper definition of guard

While reading Villette, a 19th-century novel by Charlotte Brontë, I came across the word guard used in a different way than I had known hitherto:

I was up the next morning an hour before daybreak, and finished my guard, kneeling on the dormitory floor...

From the above sentence I infer that the word carries a religious connotation—a morning prayer, a sermon or perhaps a rite.

Finding it odd, I consulted numerous online dictionaries, amongst which are Collins and findwords, but alas the search yielded no fitting result, so I resort to enlist your help.

The closest definition was 'posture of readiness or defence'; however, it doesn't coincide with the overall meaning of the sentence as I, perhaps wrongly, understand it.

The woman speaking is a Protestant, a detail that may or may not prove to be useful.

If you read on to the next paragraph, you will see that "guard" is used again: "I duly detached and re-attached it, then coiled compactly the completed guard". It seems to be some form of jewelry the narrator is crafting. It is in the form of a chain, made with silk and beads, and she completes it by attaching the clasp from her own necklace.

An example of a Victorian ladies' guard chain, worn around the neck. These were long chains, with a clasp for attaching pocket watches, lockets, spectacles and muffs.