@Fetzen
Jared was crouched down so its highly unlikely he'd be cut by glass being that a window should be at least 2 - 3 feet off the ground.
He wasn't crouched. He sat ordinarly on a stool in front of the counter for he had just delivered payment for the second beer and the room he had requested prior. Also gravity will alter the shard's trajectory significantly as long as we're not talking about really breakneck speeds (at which we'd face a bunch of other problems).
A railgun in general is pretty easy to make especially if you control electricity. You need two parallel railings that can conduct electricity being two of her fingers probably the pinky and the index finger generate a fair amount of electricity if the projectile (like a coin) can be magnetic it will jump forward the speed of which will be increased the longer it travels (You can make one in your own home with two pieces of thin iron rod, an electrical plug and a coin) just remember middle finger for B-field, thumb for direction of force, and index finger is for direction of current then match vectors.
I am aware of the principle of Lorentz' force. It doesn't have much to do with the item being magnetizeable at all. Every charged particle (that is... protons or electrons) can be subjected to Lorentz force even if it is free floating in vacuum as long as there is a relative velocity orthogonal to the magnetic field's vector. If that would not be the case we wouldn't sit here because no electric generator installed at any power plant in the world would be able to actually create electricity in its copper windigs. And several types of electric motors wouldn't work as well.
Applying the principle of Lorentz' force one can see that a railgun can't work by creating a current that flows in the coin in a circular pattern because the sum of Lorentz' forces would balance out itself. So it is like you said: The current has to be passed from a rail to the projectile, flow through it and then dumped out of the other rail. And this is the point were constructing an effective railgun capable of producting muzzle velocities we're talking about both here in theory and in your post becomes very difficult:
On one hand you have to make create a very, very good electric contact between the rails and the projectiles as possible because every resistance in the way of the current surge will generate a lot of heat: the thing could jam due to thermal expansion of the rails, it could explode because air is heated up rapidly, it could fuse together with the projectile because metals start to melt. Normally good electric contact is achieved by using soft, highly-conductive material like gold-plating (like on your PC expansion cards) in combination with a decent amount of force pressing the contact areas together to flatten any microscopic roughness. There is a reason why this stuff sometimes is a pain in the ass to insert. On the other hand you don't want much force involved, because you need low friction as well. And then all of this has to be maintained even during the violent acceleration phase.
And that's the point where your idea of using a coin-finger-combination completely falls apart.
- A coin isn't necessarily made out of good conductors. Highly probably it is even covered in smudge like fat, dirt, sweat... All of which quite poor conductors.
- The human skin resistance is in the several hundreds or even thousands of Ohms.
- You want to blast the coin out between your fingers while holding it strong enough for it not to drop ? That will generate a lot of friction (a.k.a. injury) in the firing process, added to the thermal stress caused by using high-resistance 'building materials'.
- Last but not least you don't replicate a bunch of electrons in one finger and collect them in the other. Even in a capacitor there is always as much current going out as it is going in because electrons hate each other and push themselves around if it get's crowded. So by letting a super-high current flow through your hand you'd electrocute yourself quite effectively.
- According to Newton's second axiom, you would expose yourself to the same mechanical stress as the coin (a.k.a. recoil).
Your railgun in a hand has the potential to amputate that hand in a quite violent manner. Pushing around electrons just by far isn't enough to fix the problems listed here.
If you want to dive into physics one could also consider the fact that a magnetized coin passing through a highly-conductive hunter's net at extreme speed will cause a magnetic flux going through the meshes of the net with an equally extreme time derivative. That is... it will induce currents like an electric generator. And what happens to a generator when it suddenly has to deliver a high current ? That's right, it slows down if it's no longer propelled, because it is delivering power! In this case the power is lost as warmth created by the currents in the net. If one would want to go really deep into this scenario one might shed a light on this effect as well, but I am unwilling to do that because the entire scenario is garbage.