I think that if there was an infection, it would likely seem more... Infected. IDK. I'd expect the site to look yucky, pus-y, red...
I wonder if maybe the fact that that breast was such an enthusiastic leaker early on might not indicate that it has an extremely fast flow, something your LO learned to control by biting down? Not a problem when baby just has gums, but once the teeth break through, watch out!

Letting the bad side fill up to the point where it feels full will eventually lead to reduced supply on that side. Your LO will likely compensate by nursing more on the good side. This isn't really a problem unless you start looking lopsided- and then it's only a problem if you care! If you decide to nurse more on the bad side, increased stimulation to and milk removal from the breast will increase supply to where your toddler wants it to be. Since your LO is already 19 months old, I really wouldn't worry much about supply. At this point solids are probably making up a lot of her diet, and can compensate for any lack of breastmilk intake.