" 'I cannot get out', as the starling said."

Maria's reference here is to a line from an early piece of travel writing, "A Sentimental Journey Through France and Italy" by Laurence Sterne, first published in 1768. Like "Lover's Vows" this is a work which would have been familiar to JA's contemporaries.

It seems that MP contains a good deal of veiled political satire and symbolism, and by embedding "Lovers' Vows in her narrative JA opened a rich seam of literary allusion which would have conveyed a good deal to her readers. So I strongly suspect that her choice of this quote from "A Sentimental Journey" would have conveyed an additional layer of meaning beyond the reference by Maria to the constraints of her engagement.

I freely admit that I don't know quite what JA was getting at here. The 'starling' quote references slavery, which may be relevant given that Sir Thomas has business interests in Antigua. One of the characters in "A Sentimental Journey" is named Maria, and there could be issues relating to ideas of questionable morality. I'm really not sure.

I have linked the relevant chapter of "A Sentimental Journey" at the foot of this post - the Starling quote is towards the bottom of the page. The full text of "A Sentimental Journey" can be found on-line, as well as quite a bit of contextual information and Lit. Crit.

For background information and food for thought here's a page which discusses Sterne's life and work:-

http://www.enotes.com/literary-criticism/sterne-laurence

And here is an article about "A Sentimental Journey through France and Italy":-

http://en.wikipedia.org/wiki/A_Sentimental_Journey_Through_France_and_Italy

(Sorry - couldn't get embedded links to work, so you'll need to cut & paste.)