I'd be curious to see what this was commissioned for. Looks awesome all around nonetheless. I'm not sure if this is what you were going for, but the look on Blinkie's (Please correct me if I'm wrong, for some reason I'm an idiot with these two) face makes me think that she accidentally said something to Inkie to make her upset. And if that was what you were trying for; Bravo. It looks awesome. Overall: great picture. 4/5
After Pinkamina was driven to happiness by the sonic rainboom, her father told her to leave the rock farm and not come back until she was ready to be sensible again. And Pinkamina was "Okey-dokey-lokey" and went off to Ponyville and ended up getting a job at Sugar Cube Corners and moving into a small room on the top floor. Their father told Inkie and Blinkie "I don't want to hear anything from you about Pinkamina leaving." Inkie didn't say anything and her father didn't hear her; she was sad anyway.
I've been noodling out a fanfic about what happened when Pinkie left, which also features a reunion of Pinkie Pie and her sisters. So this is just one brony's opinion.