This is my understanding of the rules relating to this situation…
As long as your claimant has been working, and been on the Worker Registration Scheme, for 12 months, you can now effectively treat her as an EEA16 national.
Her partner’s status isn’t that important, as he is a ‘family member’, and therefore shares the same right to benefit as the claimant.
Now your claimant has stopped work, you will have to decide if she is going to be an ‘unreasonable burden’ to the state’s benefit system. To do this I would probably base my decision on her intentions to find work after the baby is born.
For example, if she intends to, and is likely to, find work shortly after the baby is born, I’d say she would not be a burden. If she does not intend to look for work until her child is grown up, I’d say she is a burden.