I've been pregnant and nursing several times.
The B6 works well if taken with Unisom. The TABLETS, not the capsules. I would take one tablet at bedtime and take like half the dose of B6 the midwife suggested, then the other half of the B6 in the AM, and it really helped me with my third. The Unisom made me too sleepy to take in the day, but some moms find that a half dose of Unisom in the AM helps too. I was bordering on HE with my third through the whole pregnancy; I was throwing up until he was born. That said, I would use Zofran. It really helps
The nursling she has now, though, is nursing that much because the LO's instincts are telling her to nurse more to increase supply. The problem...supply while pregnant is NOT driven at all by demand. It is purely hormonally based. 80% or more of pregnant mamas lose their milk supply during pregnancy. Some nurslings continue nursing even though there is no milk present, others quit, others quit and come back to it. I've had all three. And the mother has no control over it. But yeah, the nursling's constant demands are very difficult. I used to feel terrible when I had to put my second child down to go throw up and the nursing sometimes made me feel physically sick.
The concern now is this really: a baby under 12 months should have the majority of its nutrition from mother's milk or formula. Not solids. Not juices. So the potential that she will need to start supplementing with something is very, very good. Watch diaper output. If wets start decreasing, then she will need to find a supplement. It doesn't have to be given in a bottle. She could use a cup or an SNS. If baby starts wanting more solids, she might want to supplement. IF baby was 11 months old, I would probably not supplement. But a 9 month old..I'd supplement.