It wouldn't bother me to keep replying to this woman, if only for the sake of your mom. Three emails ain't much and, really, in the last one the only thing she asked you was your advice on selling Dr. Who-themed stuff; I'd probably send her something back agreeing that it is, indeed, complicated, and here's a link to Etsy's policy on what can be sold (I'm sure they have something written up somewhere.)
Yeah, she's dropping a lot of hints but that kind of thing doesn't bother me. I am also a creative person and people love to try to get me in on their pet projects; I give them polite refusals (like you did) and pretend not to notice any further hinting. I've never had anyone turn nasty on me over it (knock on wood!)