On what grounds? Her making a perhaps irrational decision? Or her being at risk from miscarriage? The lines blurred quite a bit in the book.
The lines are blurred however it was clear the danger was imminent and as such it would have been a precaution to keep her in for observation as was suggested.
Pregnancy isn't an illness and doesn't need to be treated as such - however she should've been relieved of duty, not for the irrational decision she made (which I agree she is allowed to make) but for her own health and so as to prevent her condition becoming a danger to those around her.