How to reduce facial width?

At least from the one photo of the upper two-thirds of the face, it would appear that the use of a volumizing HA filler, particularly in the region of the upper, outer cheeks would significantly contribute to contouring a more ideal, oval, heart-shaped feminine face. Unfortunately, the lower third of the face is not visible,. However, in general, if enlarged masseters are contributing to the more masculine, squared appearing lower face, then masseter reduction using Botox can be considered. You would be wise to consult an experienced, board certified cosmetic dermatologist. Hope this helps and best of luck.

Fat is usually more visible in the cheeks, jowls, under the chin, and neck. Facial fat tends to be more noticeable in people with rounded and square like, less-pronounced facial features. Buccal fat removal is a surgery to remove the fat in this area of your face or cheek reduction. Contouring with dermal filler. Strategic placement of dermal fillers like Juvederm Volumna and Restylane can produce a face slimming effect. In surgery: Surgical jaw contouring can involve a facelift, neck lift, neck liposuction or adjusting the mandible (jaw bone) by reducing the bone or balancing the bone. Hope this helps.

There are several surgical and nonsurgical procedures that can help narrow the width of the face. Here are a few examples:
Surgical procedures include jaw contouring surgery which reshapes the jawbone to achieve a narrow appearance, cheek reduction surgery which includes buccal fat removal, and chin reduction surgery.
Non-surgical procedures include botox in which one injects botox into the masseter to slim the face by reducing their size, strategic placement of fillers, and neck contouring with energy-based devices.