The electrical supply for a whole house can make pretty sparks, you don't want to be near that as it could definitely kill you.
The electrical supply for a whole street can tear a noticeable crater in the street, which is why after my street lost power last year actual street repair people turned up to fill the hole and lay more asphalt as well as the electricity network people.
15A at 110V is enough to weld your tool to the wires carrying the current.
The mother probably got lucky and the neutral wire pulled away as it was cut and didn’t complete the circuit to the live wire.
The scissors must have had plastic handles that prevented the mother from becoming part of the circuit.
Do you remember if it blew a fuse or tripped a breaker?