NOT A TEACHER
Hello, Mike:
Yes, according to some sources, you are right.
"She seems
confident that she will be chosen."
Pence and Emery in
A Grammar of Present-Day Grammar (1947 and 1963), pages 179 - 180, feel that "that she will be chosen" is an adverbial clause that modifies the adjective "confident."
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Here is another view held by some sources, such as House and Harman in
Descriptive English Grammar (1931 and 1950), pages 379 -380.
"I am
afraid that he will refuse the offer."
They feel that "that he will refuse the offer" is a noun clause that is being used as an adverb.
They feel that "I am afraid that he will refuse the offer" is a shorter way to say "I am afraid [of this] that he will refuse the offer."
As you can see, "that he will refuse the offer" is a noun clause in apposition with the word "this."
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Pence and Emery feel that it is simpler to just call such clauses "adverbial clauses" instead of saying that they are noun clauses being used as an adverb.