Ella, I'm looking at Clara as one of the new liberated, independent women at the turn of the century. She did give notice at Tiffany's to marry Edwin, but notice that she didn't marry him. She has reservations about his ability to excite her, perhaps? He's not high spirted, like George. Do you suppose she was giving Edwin an audition to see if they were compatible, if she wanted to actually marry him?
Now that Edwin is gone, she can admit to herself there was something to that the dream in Nutley (that she was marrying George, and not Edwin) Now her heart is breaking over the loss of Edwin.
Do we know what kind of doctor, the boarder, Dr. Griggs is? Remember Clara asked him if he thought Edwin might be alive - and just lost? Dr. Grigg's tells her that if he had an illness or a disorder, he might not have the sense to nourish himself, or take care of himself. But if he left intentionally, the doctor tells her, he might have a plan, so he's probably all right.
Which do you think happened?
As long as Clara believes that he left intentionally, he might be alright - and return. If she really believes this, she can't move on and become interested in another man. Not Mr. Belknap, with his opera tickets, or the Booth brothers...or anyone else. But she can throw herself into her work and Mr. Tiffany.