I can figure out where she is heading means I can figure out where she is going Where are you heading? means Where are you going? Heading when used as a verb like this, means "going"

One of the meanings of "heading" is "compass direction," "course," or "destination:" "the ship is heading northeast," "the family is in the car, headed for the amusement park." In your phrase, it could be meant literally: "She has library books under her arm, I can figure out where she is heading." It can also be figurative, your planned "destination" in an argument or discussion. "Emerging markets countries have the fastest economic growth. However, everybody knows that, so, according to the efficient market hypothesis--" "Oh, I know where you're heading. You're going to say that the information is already priced in."

Many words in English can be used as both verbs and nouns, sometimes with completely different meanings. What you found in the dictionary was the meaning of "heading" as a noun. But in your sentence, "heading" is from the verb "to head". It refers to the direction of travel, where someone is going.

Heading 的其中一个意思是 "方向". Where are you heading to? Head north and then make a right turn.

You are almost correct. "Heading" in this sentence means "the direction she is going," or "her destination."