Well, I tried to embed a gif, and it didn't work.

I have a clear limit to the effects in mind, but I'm not quite sure how to voice it. If you're familiar with the anime World Trigger. A powered down version of Chika in terms of her projectiles. As for shapes, I was thinking mainly between small armor piercing for thicker armor, weaker barrage as the bullet splits up, a standard sniper round, and a slow beam with little penetrating power but large damage. The time between shots would also be slower than the faster swinging speeds of her allies. 

As for the shields, I imagine a one meter by one meter cube. The denser that cube, the stronger it is. Inversely the more she spreads it out, the less it can block against. Ideally she could defend against artillery's shells with it when it takes a direct hit protecting against only one direction if that makes sense.

It might also help to explain that she can only do one or the other. Trying to split them between fire power and shields would leave both less than effective.