That's not because of the botox. The sagging will happen anyway and is down to face shape/bone structure, weight and other factors.
Majority of threads with jowls, sagging, and other signs of ageing, don't involve botox.
Botox plays a role in this "sagging". As does rapid/extreme weightloss, and bone structure, some genetics and skin types, and smoking, alcohol, excessive sugar intake, and sun damage. But most of what has apparently "sagged" is muscle tissue. I cannot help noticing that many women of middle age have what I would term "misery face" at a certain point, which they elect to "fix" not by improving their mental attitude and lifestyle, but by these procedures.
I do think Botox is a gateway drug. You are entering a world where these procedures are normalised, and you are focusing on a displeasing feature which then, care of your excessive focus or the side-effects of your previous "tweak" leads to you noticing another area of concern.
As I wrote in another Botox thread:
It is odd, as Botox freezes the muscles of the face, and so expressions aren't made or made as fully. But the Botoxed muscles atrophy over time, and then everything sags. This is attributed to "loss of fat pads", and "ageing", and then fillers are "needed". Then the fillers migrate and things start to look a little puffy and strange... It's a look. Many like this look. But it isn't youthful.