Weird jellyroll while wearing spaghetti straps?
It can also be muscle. For woman doing some weight training and not being on a low bodyfat it can kind of look like a side boob. What you can do are change all flatt chest exercises for incline ones. This because these exercises will somewhat more focus on the attachment point of the chest muscle and upward. Instead of downward. Dont expect major difference but over some time it will give some results.