Why yes, I did make her look like she's plausibly related to Pinkie Pie.
Nah seriously though I think it'd be fun if Peachy was Pinkie's cousin. I think the Pie family has a few weird genetic traits that are passed down the family and only pop up every now and again. Any foals born to the family with these traits are pretty much guaranteed not to inherit the farm, so they go off and lead their own lives separate from the rock farm (like Pinkie).
Peachy here, I think, is the daughter of Igneous Rock Pie's sister, Pearlescent Pie, who left the rock farm and married a farmer (not a member of the Apple Family). They had a good few kids between them, and Peachy here is one of them. As much as she looks like Pinkie, though, she's not the same personality-wise. Peachy is just as kind and friendly, and she also loves making ponies happy, but she's a fair bit quieter about it. Peachy is the kinda cutie who'll approach you shyly and ask if you're okay and try to fix whatever she can or point you in the direction of someone who'll be more helpful. She's a lot more sensitive to other people's feelings than Pinkie, and also respects their wishes a lot more often if they want her to leave them alone.
I, uh, don't really have much else here; she's basically just a bit of a bare-bones personality at the moment and I haven't stopped to consider exactly what she does in day to day life and what her profession is so… yeah. See you next time :D