My theory, from what I've seen of the show and previews (I thought of this before I remember Rebecca's "peanut" thing :
Dev proposes to Karen. She turns him down. He has his a-hole "after all I've done for you" moment, they part. She quits the show to show her love for him. She catches him with his co-worker, they call it quits. She's out of luck.
Ivy catches Derek with Rebecca, turns out Rebecca came on to Derek and he fires her. Ivy gets Marilyn. She pops some pills out of nerves and has a reaction and has the emergency "SHE CAN'T BREATHE", therefore being unable to go on.
And just when you think Lil Miss Iowa is out of luck, she's MARILYN!
If it seems highly unlikely, look at how this godawful show is written. Just a thought.
I don't WANT to live in what they call "a certain way." In the first place I'd be no good at it and besides that I don't want to be identified with any one class of people. I want to live every whichway, among all kinds---and know them---and understand them---and love them---THAT's what I want! - Philip Barry (Holiday)