I'm 5 feet even and I can tell you when I looked for an aero bike, small enough was hard to find… I do not have a long torso or arms, so my bikes generally need to be shorter in the top tube, which can be hard to find in a TT bike.
What I did eventually find is that one of the few manufacturers who at the time made very small bikes was Quintanaroo and they make nothing but tri-bikes so they've bikes at many price points. If you can find a dealer in your area they do their XS that may well work for her- she might possibly even only need the small. I know other relatively small people with a bit of a different body type than mine (longer torso/arms) that have been very happy with the smallest Cervelos.

btw.. the way the message board truncates your title it reads - Hubby looking for advice on buying the most amazing women in the world….