What is she talking about? What's the magic beans? What's the riddle?

She’s referencing multiple fairy tales common to the English speaking world, including Jack and the Beanstalk (in which a boy buys magic beans) and various tales of Bridge Trolls who make you solve a riddle before crossing the bridge. 

It’s a joke based on common fairytale tropes in English-speaking folklore. Trolls under bridges, magic beans/vegetables, trolls asking riddles/questions. It also might be a joke about TSA/law enforcement stopping people to check for ID, but it’s “the one fucking day I leave the house without them [magic beans/ID]. That might be reading too far into it. Essentially, it’s all just a misdirect.

She is being satirical. She is creating an absurd, fictional story which also contains elements of the real world for comedy effect. The 'troll' is a mythical character, a giant monster that lives under bridges. However, in modern internet vocabulary, a 'troll' is also a person who enjoys mocking and attacking others. The 'magic beans' are a feature of fairy tales, namely 'Jack and the Beanstalk'. She starts the story acting as if she is distressed about a true situation. When she mentions the troll and the beans, the audience knows it's a fantasy story, but then she introduces the joke 'dragon these balls across your face', which is a rude sexual joke that you would only see in the modern world. She subverts the audience's expectations several times, and this is why it is comedic.

It’s a joke with multiple layers 1) the primary layer is that she is poking fun of “travel influencers.” The video starts off with her saying “if you’re a young person traveling by yourself, just be so careful” while looking upset. You think she is going to be sharing a traumatic travel experience as a warning for others. 2) she says she comes across a troll under a bridge. This is a fairy tale archetype, where a troll hides under a bridge and doesn’t let the hero of the story cross without passing some sort of test, like paying gold or solving a riddle. 3) she says the troll asks for magic beans. “Magic beans” are an important plot item in “Jack and the Beanstalk” and derivative works. Because that story is so well-known, “magic beans” are also an archetypal, generic “magic but mundane” item. 4) she says this is the one day she left the house without her beans. It’s just a little joke about inconveniences that seem to line up perfectly against you. Like when the credit card reader at the is not functioning on the one day you don’t have cash with you. She offers the archetypal riddle as an alternative. 5) “Dragon” sounds like “draggin(g).” The troll says “dragon” as bait, which she takes, and he derides her by saying “Dragon deez nuts across your face” (I.e., “dragging these nuts across your face”)

I’m surprised you were on tik-tok trying to make sense of any madness you found there. Most people just swipe away.