I see there is more than grammar function for a clause of (that ) Here is example :
She could not accept the reality that her father had died.
One grammar book tells ( that her father had died ) = appositive OK I agree with because it can rename the word noun ( reality )
2- I see it looks like adjective telling ( which reality ) or giving further information about it, so it can function as adjective answers the question ( which reality we are telling about ) This idea I so far agree with
3- I can also say it can be a ( predicate nominative ) likely ( object complement ) This idea I say perhaps but not object complement ((because object or subject complement are usually adjectives )). We can say a part of the predicate Sorry I am wrong with this. I didn't look the verb first. That clause can be predicate nominative only with linking verbs.
Many books tell that a reduced relative clause can be appositives, but here it is not reduced
The problem is always with clause of that since it can be both (( noun clause and adjective clause )) (No doubt, It has many functions grammar)
So, can excellent user give me a little guidance ?
Thank you in advance