I have to say that knowing that Stacy didn't encourage an interested 9 year old kid to talk to her really colored my opinion of her. That's a shame, really, that she didn't find a snippet of energy to encourage a kid, no matter how bad her day was. But I'm also speaking as a mom of a 10 year old kid. I would've told my kid not to expect anything, but I would've been taken aback by her reaction as described.
One of my kid's trainers was like that--low energy, seldom smiled, never volunteered a bit of information, though did answer questions. She was positive in lessons and didn't yell or anything like that. For a while we just accepted her for what she was--not a people's person. Everything was fine. Only after changing barns we realized how emotionally draining that trainer was. It is difficult to be with a person who struggles to communicate.
I read some of Stacy's blog some years ago, and I was also turned off by her grammatical errors and poor spelling. Not a big deal, really, but she doesn't seem to be a skilled communicator. And that's okay. There are plenty of trainers who are selling their brand more effectively, for better or for worse. There's choice.
I agree that the OP shouldn't have expected personal attention or to be friends with Stacy, but empathize with the OP.