Like Snobby, Rummy has figured out that she's of a lot more interest to the Salvation Army "lasses" if she makes her story out to be more horrific than it actually is. As she tells Snobby:
What am I to do? I can't starve. Them Salvation lasses is dear good girls; but the better you are, the worse they likes to think you were before they rescued you. Why shouldn't they av a bit o credit, poor loves? they're worn to rags by their work. And where would they get the money to rescue us if we was to let on we're no worse than other people? You know what ladies and gentlemen are. (2.17)
So, yeah, she lies to help out the "lasses"…and eat, of course. Naturally, the lasses (e.g., Barbara) don't have a clue.