In Newtonian doctrine, a spherical object, like earth, attracts -as if- all its mass is concentrated at its center. So, if her reasoning is correct, the earth must already be a black hole, because all its mass is supposed to be concentrated at its center.
So the escape velocity from earth at its surface is well below the speed of light. And below the surface, gravity is even less. Only a black hole packs enough mass into a small enough place to get the escape velocity above the speed of light.
attracts -as if- all its mass is concentrated at its center
At a radius _inside_ the object, only the mass closer to the origin counts so the "effective" mass of the object drops smoothly to zero.
And yes as far as anything else in the solar system is concerned, if the earth was compressed into a blackhole no orbits would change. Well relativistic effects mean there's no stable orbits below 2 radii (maybe it's 1.5), so various sats would get sucked in.
However just because that's true, doesn't imply the earth is a blackhole, just that the orbits in the solar system wouldn't change. Similarly if the sun collapsed into a blackhole the earth's orbit wouldn't change, but it would get much colder.