Okay, looked at other pictures, still not sure if this is shell rot or not - we are worried that we've been keeping the cool side of her enclosure too damp, there's been mold on her leftover food some mornings. Please take a look. Thank you for any advice!
Since one of the causes of shell rot is the tortoise sitting on wet substrate, the most frequently seen START of shell rot is on the plastron (bottom shell). You hardly ever see it starting on the carapace (top shell).
Looks normal. Try giving her a soak and using a toothbrush to gently scrub at the discolorations. It looks like dry flakey scutes or maybe a little dirty. She is starting to pyramid just a smidge, how is your humidity? I would use a fully enclosed enclosure while she's little. She's very cute, I wanna see her face now! Oh yay, Yvonne stepped in here, I'm glad because I'm not super knowledgeable.
Thanks, guys! She gets a soak daily, we'll make sure that we give her shell a little scrub next time. Our humidity ranges are good, usually on the high side if anything, the pyramiding was there when we got her a year ago and we're working on getting it smoothed out - she is doing better! It used to be a lot more pronounced. We did get her from PetSmart, so yeah.