Alibaba just isn't good with girls.
Morgiana can tell. It's okay, honestly. She doesn't think herself terribly good with boys, either, especially not the ones in Sindria at all of the festivals and parties that ask her for a dance. They aren't like Aladdin—young and sweet-faced—and they certainly aren't like Alibaba—older and sort of awkward. They smile and take her hand and already know how to dance, and it makes her self-conscious and unsure with every step, even if she likes learning, all the same.
Maybe one day she'll know the dances well enough, and can show that to a pleasantly surprised Alibaba. That's assuming, of course, that he ever asks her.
It's okay if he doesn't, though. He has many other things ahead of him, a dozen responsibilities as a prince that she can't quite fathom, and it's moreimportant for him to go and become stronger (though even if he didn't do that, and stayed within Sindria and got fat, she'd probably still like him, and want to protect him). She has her own things to do, too, and so even when it's sad that he isn't near her, being awkward and not quite good at… well, much of anything (especially girls), Morgiana still doesn't think she has much of a problem with waiting.
Eventually, maybe they'll all get to go back to Sindria together, enjoy another festival night, and she won't be quite so worried about being asked to dance, because it'll be Alibaba doing the asking.