Learn Danish: Hun er oprindeligt fra Tyskland. - She is originally from Germany.

Because it is being used as an adverb. In Danish, when you turn an adjective like oprindelig (original) into an adverb (originally) to describe an action or state, you add a -t to the end of the base word.

How do you break down the word Tyskland?

Tyskland is formed by combining the adjective tysk (German) and the noun land (country). You will see this literal "[Adjective] + land" pattern in several other Danish country names, such as Rusland (Russia) and Grækenland (Greece).

Could I use af instead of fra to say she is "from" Germany?

No, you must use fra when talking about geographical origin, hometowns, or traveling from a location. The preposition af can sometimes translate to "from" or "of" in English, but in Danish it is primarily used to describe what a physical object is made of (like a table made of wood) or who created a piece of art or literature.