Was there a dropped (or missed) plot twist? (Spoiler)

When Mrs. Prentiss goes to Thorpe to do something about her daughter's infidelity, Thorpe mistakenly thinks she's talking about the problems he's having with his stenographer Betty, who is threatening to sue him for (a forged) breach of promise.

I figured, "Aha! Mrs. Prentiss will demand that he "marry her immediately." He will think she's telling him to marry Betty. Betty would then either have to go through with it, or chicken out, and in either case she'd have no more breach of promise to threaten him with.

If Betty did marry him, a happy ending for the two could be suggested, and Ann would be free to marry Dick. If Betty backed out, a grateful Thornton could free Ann to marry her choice (since Ann's mother suggested he marry someone else anyway), or Ann could reasonably refuse to play second fiddle.

This plot development seems to obvious to me that I wonder if was proposed but dropped for some reason. Or did this twist occur to me only?