It is easy to see why Edmund thought "Lover's Vows" a most unsuitable choice of play for them all, and especially for Maria in her "delicate situation" as an engaged woman. Maria plays Agatha, a fallen woman who was seduced in her youth and is now destitute.

In the very first scene she has a clinging (though not passionate) embrace with her illegitimate son, played by Henry. No wonder Both Maria and Julia wanted the part!
Describing her seduction, she says: "His flattery made me vain, and his repeated vows .....I was intoxicated by the fervent caresses of a young, inexperienced, capricious man, and did not recover from the delirium till it was too late." Indelicate stuff indeed!

Though quite unsuitable for the Mansfield crowd, "Lovers' Vows" was very fit for Austen's purposes. Several versions were published 1798-1800. The version JA uses is the translation by Mrs Inchbald, which would have been very familiar to JA's contemporary readers

There are obvious correspondences between some characters and the people who play them. Amelia, played by Mary, is a very forward young woman who loves Ahnalt (Edmund), a virtuous young priest. Check out Act III scene 2, in which she manoeuvers Anhalt into confessing his love for her.

The play is also full of indirect references to the character and situation of people at Mansfield:-

Agatha, born to a poor but respectable family, was taken at age 14 to live with the wealthy Baron's family and taught to be a gentlewoman. (c.f. Fanny).

In Act II scene 2, Amelia's conversation with her father about the wealthy Count who hopes to marry her is hilariously reminiscent of Maria's attitude to poor Mr Rushworth.

At the end of the same scene the Baron speaks of his dissolute youth:
"A man is sometimes tempted to commit such depravity when young. ..... In my youth .... I had no instructor but my passions; no governor but my own will." Hmm - Remind you of anyone??