Lots of protien is key for mama and I think keeping them seperate is best for now... She needs the least amount of stress possible, plus if you haven't already you have to complete the 30 quarantine and 2 vet checks....
If she is acting lethargic, please check hydration levels by pinching the back of her neck, if the skin stays up, you'll need to get her onto some liquids ASAP....
You may also want to get a joey rejection kit, just to be ready.... Congrats on the little one ^.^