As
@CaseyTatumm said above, almost all congenital umbilical hernias resolve themselves in the first few years of life, with around 85% spontaneously closing by age 5. The vast majority are completely asymptomatic and require no treatment. It's difficult to see how large Skylan's is from that photo alone, but fascial defects larger than 1.5 centimeters (slightly over 0.5 inches) in diameter are less likely to go away on their own. Even if hers doesn't resolve itself, the surgery is relatively straightforward, and unless the hernia becomes symptomatic, it can wait until she's a bit older.
Of course, umbilical hernia can also be a sign of a bigger problem, but for now, we can assume it's benign.