This "iron-haired old woman" (5.55) drives a brightly-painted gypsy wagon around Faerie, parking it by Wall for the market once every nine years. She sells beautiful glass flowers, and she has a lovely shop assistant.
So far so good, right? She sounds totally normal, right? Check out what she says to the witch-queen who pulls up to her camp:
"I should tell ye that I'm just a poor old flower-seller, a harmless old biddy who's never done nothing to no one, and that the sight of a grand and terrifying lady such as yourself fills me with dread and fear." (5.57)
That's laying it on a bit thick, don't you think? Still, it gets an oath out of the witch-queen to not harm her, and there are few people who can claim the same. She introduces herself as Mistress Semele, but the witch-queen remembers, "They called you Ditchwater Sal, when you were a young chit of a thing" (5.69). That's not a particularly refined sounding name, so we're guessing that Mistress Semele pulled herself up by her bootstraps to make a life for herself.
She sure complains a lot, though. She says of her servant: "'That bird gave away one of the prizes of my stock of items for sale, gave it away to a good-for-nothing, nearly twenty years ago. And afterward, the trouble she put me through scarcely bears considering'" (5.66). Meaning, her booth slave got pregnant, and instead of viewing it as a cool life event, Mistress Semele saw it as an inconvenience.
Madame Semele physically abuses her slave, or at least she did in the past. When the slave observes that the chain is growing thinner, Madame Semele remarks, "'I thought I had long since beaten all of your insolence out of you'" (10.108). Ugh. She doesn't even front like she's benevolent.
And she verbally abuses her, too. When the chain fully evaporates, Madame Semele tries to play the helpless card, saying, "'But what shall I do? I am old. I cannot manage this stall by myself. You are an evil, foolish slattern, to so desert me like this'" (10.160). Ouch. But Lady Una, no longer a slave, isn't falling for this drivel and instead drives an apology from her. Will Madame Semele learn to be more polite in the future? We're not counting on it.
Say what you will about Madame Semele, she can be pretty sly. She tricks the witch-queen into eating limbus grass, which causes her to tell the truth whenever she speaks for a few hours. That's how Madame Semele learns about the star, which she now wants in order to restore her own youth. The witch-queen casts a true-speaking spell to prevent Madame Semele from ever learning of the star's location, but we've still got to hand it to her for pulling one on the witch-queen.
She's quick to take offense, too. Like when Tristran frees the bird (who's actually his mom) from being all tangled up, Madame Semele shouts at him:
"I shall turn your bones to ice and roast you in front of a fire! I shall pluck your eyes out and tie one to a herring and t'other to a seagull, so the twin sights of sea and sky shall take you into madness!" (8.131)
We give her props for being creative, but more than that we give her props for the fact that, once she finally figures out that Tristran isn't a thief, she stops shouting threats at him, and even apologizes.
But then there's the matter of the glass snowdrop that Tristran trades for passage to Wall in her caravan. He thinks he's being all clever, making her promise to deliver him safely, and in the same condition that he starts the journey in. But it actually just means that she's able to transform him into a dormouse (which eats less and weighs less than a human), and turn him back into human form again when the journey's over. Oh well, it's hard to pull one over on Madame Semele.