Door drips water?

Hmm, looks like bird poo.

The water is going to drip out regardless. They are not identical, there will always be subtle differences is sealers, paint, seal quality and more. Just the nature of mass production. If you were to strip them into all the pieces you might find 20 parts out of the thousands that are actually the same, and then you would need for them to be assembled exactly the same. Never going to happen because everything has tolerances in fit and finish materials and more. That is why the door seals are rubber, why every hole in every panel is slightly larger than the bolts that go through them. All needed to make them all fit and be as cheap as possible to maximize profit at sale.
Then you have location. Her car may have been parked at a slightly different angle, the tires may have had higher pressure due to sunlight or heat. The wind might have pushed the rain at a different angle, if they were parked near each other the air currents around them will influence the rain. What you are seeing is 100% normal. Want an example - Go into any clothing store, pick out 10 items of a garment, compare them, Those are at most 20 pieces assembled to a pattern, find any 2 that are actually the same. Not going to happen. Same thing with cars. There are tens of thousands of variables in them and how they respond to the environment is one of them. The more rain you have, the more water has to get out. There will also be some water that gets trapped because of the vehicles position. The drains are designed to work when the car is perfectly level. Now say the inner panel is crimped just a tiny bit different where it attaches to the outer skin, now the drain might not be in the exact spot to drain out all the water, then the car is moved or the sun shines on it and the materials shift around and now that water can get out. No different than everything else, her radio might be louder, the engine in yours might be smoother, the tires might wear better. All due to those tiny differences. She's your grandmother which means you share her DNA, do you look act and think exactly the way she does? I'm going to bet you don't. No different with cars and car parts.

Every day = airflow through the vents and body and that will blow water around and dry it out faster as well. Probably not a bad idea if you have 2 and hers sets around to do what I do. Alternate driving them. Keeps them limber and dries out anything that might get damp. Also confuses the rodents.

Good to hear you have kept the rodents away. Leaves are not an issue, If you want just brush them off. They won't hurt anything. Probably drop off when they dry out anyway. Like many newer cars they don't actually draw much air through the grill, 99% of the air actually gets pulled in from under the front end.

Nope, not an issue. You can remove them with whatever you like. I usually blow the bugs and dirt out with an air wand on my compressor, but that isn't something that most people own. But if you can see them a pair of long tweezers or even a feather duster to get them out. That or let them dry out and they will fall out sooner or later.

Looks like a discarded cocoon, look in the trees around where you drive for a bagworm nest, they leave ones like that when they hatch. Questions are handled on a first come first serve basis. If a new one pops up someone grabs it.

Probably blew in from the work around you. Just give it a good bath and a nice coat of wax and that would help with anything sticking to it. Just don't use my vehicles as an example, I haven't wash or waxed a vehicle I own in a very, very long time. Usually they rot away underneath long before the paint fades around here. Poo would be solid, not just a husk.