Just wanted to play devil's advocate here
Two things immediately popped into my brain:
1) I've been on Etsy for about 4 years, and I've learned that as a seller, you can NOT please everyone. For example, some buyers expect a seller to convo them immediately after the sale to thank them etc, whereas other buyers get outright angry if you convo them, as they consider it spam. So, while you may have expected a convo'ed response, the seller may
have considered the feedback she left as her response and didn't want to "spam" you.
2) Artists are notorious for not being able to take compliments. Most of us immediately want to downplay anything positive you've said about the work, but that is very counterproductive for a business selling artwork, especially if you put down your work in front of someone who just bought it.
So she may honestly have not known how to say thank you without feeling awkward.
Of course, there are really any number of other reasons that are possible, and I do think she should have responded. But I have a tendency to always try to give the benefit of the doubt.
You have every right to be disappointed at the lack of response, but I wouldn't necessarily give up on her yet if you really do like her work.