When Bailey's Comet is shown passing, the light shifts through the windows at a very rapid rate. While comets are frequently close to 20,000 mph as they pass Earth, they would have to be extremely close to Earth, within the atmosphere, to create an effect like that. They actually take days and weeks to pass through the sky. This type of error is frequently shown in shows involving comets. The effect in this show is similar to Night of the Comet (1984).
The light shining through the windows as Bailey's Comet passes has a yellow or orange glow, similar to a fire. Comets are not fireballs and only cast reflected light similar to the moon. Due to their small size, they would cast very little light on towns and houses except of a moonless night.
Abigail mentions that her brother is fighting on the Western Front. The Western Front was the decisive front during the First World War and did not take place in 1892 (Abigail's time period). However, as Rivervale is a 'parallel' world, perhaps there was a Western Front in Abigail's time.