Could have done better with Morgona!

Wasn't that the point? I mean, she talks about how her mother liked URSULA better, and how the 2 sisters are always been compared (with URSULA winning everytime).

I know, she was basically just a skinny Ursula. That's the problem with these DTV sequels is they lack creativity. It's usually having to do with the child of the protagonist having basically the exact same adventure as in the first movie. Or in this case, the direct inverse (human wanting to be a mermaid). I'm just glad that Disney finally had the good sense to stop making these things!

Well, I really hated Morgana due to her being an annoying manchild, and in fact, she was one of the reasons I ended up quitting watching the film (though I hear she was improved upon in the Special Edition, so we'll see).

That being said, at least she was a far better done villain than, say, Marina del Ray from Ariel's Beginning (sorry, but she just came across as more of a victim and didn't really come across as all that threatening, only wanting a promotion, while Morgana at least did try to murder a baby/pre-teen girl in cold blood while at the same time actually trying to conquer a kingdom), and certainly she was better written than Kylo Ren in Star Wars: Episode VII The Force Awakens (I hated his characterization in the film for pretty much the same reasons why I hated Morgana, only unlike Morgana, he doesn't even have an excuse for his being poorly written or especially his characterization).

I didn't mind the character, but her introduction was a joke. The moment she appears, Sebastian remarks, "it's Ursula's crazy sister!" Um...WHAT? Okay, Ursula had a previously unmentioned sister. This sounds like a Wicked Witch situation, where after the Witch of the East is killed, we meet her sister, the Wicked Witch of the West, who is worse. That's how the Wizard of Oz played it, except in that case, the Witch of the East wasn't a previous established character.
Bottom line, that "Ursula's crazy sister" line didn't need to be there. Let her introduce herself.