I'm not much into masks, but I have to say that it's great work for an 11-year old. Therians are a very niche group, and not all therians enjoy wearing masks. So IF she wants to sell masks, she should market them broader, in my opinion. Furries, LARPers, cosplayers, etc. Most of all, I think a child should make art and be involved in their hobby because it's fun and creative, not to make money.

And about possible connections between ASD and therianthropy... According to some earlier commnity surveys, neurodivergence is more common among therians than in the general populace. But note, those are self-reported numbers. Here's some links to old survey results: https://www.reddit.com/r/Therian/comments/159k7c0/some_older_surveys_and_their_results/

This research article might interest you: https://irep.ntu.ac.uk/id/eprint/34612/1/12131_1131a_Roxburgh.pdf
According to it, therians were more likely to score high on an questionnaire used to map autistic traits, and were more likely to have been diagnosed with a mental illness, compared to non-therians. But the sample size is kind of small (112 therianthropes and 265 non-therians).
Here's links to more scholarly papers about therianthropy and otherkinity:
https://www.reddit.com/r/TherianAdult/comments/196brn9/xpost_from_rtherian_research_papers_relevant_to/

I'm an adult therian, but not autistic. I can even say it with confidence, since I went through a long psych evaluation (I thought I might be on the spectrum) and came out negative, lol. I often bring that up as the danger with self-diagnosis: before the evaluation I was pretty much convinced, and I think I experienced quite a lot of nocebo because of that. I've had some issues with anxiety and depression over my life, but as far as I can tell, I'm neurotypical.