OP, I agree with you that the concrete pad is too close for the pit. However if you place one further back you will be in what looks like the drainage ditch behind the properties or on a slope which is not conducive to sitting
Install permanently a couple of those cement curbs seen in parking lots everywhere. You can easily sweep and squeegee around them. If she drives over 2X4 then these may solve the problem.
A light is not going to work- she’s going to go until the car is stopped by something.
It may be a 10 hr job, but when the plumber comes out he will have a helper and now you are talking 20 hrs labor. They will bill what they can get away with.
Put 8-10 drops of peppermint oil in a 16oz spray bottle filled with water. Spray that around entries to your garage,along baseboards and in corners. Repeat every couple months.