Well way to go new girl!! She's been there how long? And decides right at the last minute that the pregnant woman can keep doing the job that is too hard for her - not on!

I agree with everything Lulu has said. You've done your best, you've helped out their business massively, but it's time for you to come first. Realistically, you don't have long left with just you and your DD, or just time to yourself to nest and relax. You've done the hard yards and deserve a break!

I'm sure your boss will understand, and like Lulu said, it's not like you'll be able to stay long enough to to find and completely train a new person anyway, so you may as well divvy up the work and leave when you were supposed to.

Good luck!