I don't think you body-shamed Cassie or said anything that could be considered as such. Sure, it's not appropriate to comment on someone's weight, height, etc. But at least your comment didn't come from malice.

I've learned a long time ago not to comment on people being thin, chubby, fat, tall, short, etc. I had a coworker in the past who was 6'8, and everyone would comment on his height all the time. It was so annoying to me, because I saw his reaction; he surely suffered from these comments and feeling inadequate his entire life. It's great that we, as a society, established that commenting on weight is not okay, but I wish we'd make the same conclusion about weight.