Breast-fed babies' eczema could be triggered by what the mum is eating. Is she feeding baby herself? If so, she might find it helpful to make a food diary to spot any patterns, flare-ups etc. Number 1 irritant is dairy, but doctors are very wary of avoiding this when breast-feeding. Replacing it with goat's milk is the best to try as it's broken down in the same way by baby. Also, never forget that calcium is present in other foods too!! Dark green leafy veg is a great source, for instance. (Cows eat grass, after all...) Your sister can get plenty that way and pass it on in the milk without having dairy herself. The jury is still out on soya for mums/babies. It's possible to feed baby the goat's milk directly, if mum's not breastfeeding, but she'd need to ok this with the Health Visitor.
If your sister's not comfortable with any of that and wants to stick with creams - try Allergenics steroid-free (health food store) or Diprobase (prescribed). We're a bit of a sensitive family, and I have to say that I find Diprobase the best by miles! E45 has never worked for me or my son, and Aqueous cream is great when it's dry and itchy, but not when it's weepy, sore or red. It sounds like this isn't helping at all at the moment.
Your sister has to think along these lines - that any external reaction on the skin is a sign that something is not right internally with the digestion. Think from the inside out!! The things that trigger baby's eczema now will probably be things to avoid in childhood too, so the sooner she can pinpoint them, the better!
Maybe find a doctor who's a little bit more well-rounded, no offence, doc! This complaint is so common, and these days doctors should be more open to alternative remedies. It's not quackery! Failing that, do all the research before seeing the doc, so that he can see it's being taken seriously. It's all too easy to say, "baby will grow out of it," and not actually do anything for you, I'm