She will still get less sick because she will get your antibodies to any "family bugs"...

there is also some evidence that babies who are BF while they are starting solid foods have lower rates on average of allergies than FF bubs

It's not really clear to me how much BM is needed for these things to happen - i.e. if you were to ask me whether Arlea would get the same benefits from 200ml/day or 800ml/day I couldn't answer you!