maybe you can make it seem that you are suggesting that she not stay for her sake ie the baby will be up at all hours and we don't want you to exhaust yourself trying to help, you're sure that her and her BF will want the privacy of thier own home and be more comfy in thier own bed.
Or maybe you can make it seem that it will be better/healthier for you if she is at a distance ie you need somewhere outside the home that you can visit and just be yourself so that you don't feel homebound but at the same time don't feel pressured to be all dressed up etc (like a home away from home).
I think if you try to emphasise that you will really need her support and downplay the don't want her staying factor it will be less likely to offend. I'm sure that she wants to help so maybe you can suggest some things that she can do for you from her own home ie cook some meals for the first week or so that you are out of hospital and bring them over or do some shopping for you.
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