Zeagles are nice because they use a modular system. This means that you can mix and match different sized components of the BC to get a perfect fit. They can also make a custom size if needed. The other main feature of a Zena that makes it different is that it uses a zip-up vest, as opposed to a cummerbund, to secure the front of the BC. My wife likes her Zena. But, the truth of the matter is, you really need to have your wife try one on. For that matter, she should try on several different makes and models. Within the 2 most common types of BC's, jacket and back-inflate, there are just to many options designed for woman and there is no standard. It's whatever she feels comfortable in. If all you're looking for is a sure-fire fit from an off-the-shelf BC, then the only recommendation I could give would be a BP/W. But I can't guarantee her comfort in it.
I do have a question that might be helpful in answering your question. What differentiates a petite Asian woman from any other petite woman? Since you added that qualifier I assume that there's some feature that is unique that we should be focused on.