How to make my jaw less square (female)? (Photos)

What you seeking is traditional V line surgery where the back of the jaw angles are vertically reduced combined with a vertical chin lengthening and narrowing. While this can be effectively done the tradeoff is almost always some slight sagging of the soft tissues along the jawline.

Your research would be the 'V-line' surgery which narrows the back/ramus; (don't change the actual 'angle) and tapers/narrows the chin. Common approach and if done artistically, will yield the type of contours you propose