Here's an Inked, colored, and shaded version with a background made in Photoshop. I tried to clean it up as best I could, but I'm not totally happy with it. But I thought I'd use it to practice coloring and shading.

The story behind the pic is, Sandra ran up to Supergirl to tell her how awesome she is, being a fangirl, and somehow talked Supergirl in demonstrating her strength. It was an innocent enough lift, that ended up someone inappropriate. Anyhow, after being lifted, Sandra discovered a few things about herself that day.

The original sketch can be found here.

Sandra Tilton © magictowers

Supergirl © DC Comics