You can Estimate what 2019 will look like and calculate the quarterly estimates. This isn't Fact: "Aside from the penalty she owes a lot and her normal income cant pay what proseries is calculating her payments each quarter in 2019"

It's using the reference data from the 2018 tax preparation. If 2019 will be significantly different, you help the client by figuring out their most likely requirement for 2019 estimates.