I say ......
I wouldn't expect her to wear them much at all now, unless she a determined women or genetically lucky, and who manages to get back to her original pre-baby weight/size. I've made no secret of my theory that as a persons weight increases, typically it spreads the owners foot dimensions. This is somewhat supported by remarks seen on listings where heels are sold on, because their owners no longer fit or can no longer tolerate high heeled shoes.
I'll be happy to be wrong about my expectation.