My retic has been going through little swollen upper lip/nose swelling spurts that looks much like your pics. Her jaws are completely normal but she would open up a little wound right there in the front and it would swell outward that would make it look like her lower jaw was smaller. Diluted betadine swabs to the area got her all fixed up and her mouth goes back to normal.
Has her lower jaw ever looked "off" before or just now? I'm not sure what those little marks are on the lower lip line.