Janice was abused by her father.
This is a grammatical sentence, with a subject and predicate. It says that something happened, as a matter of fact.
She asked about X.
The X represents the object of her questioning, which in this case is the fact that Janice was abused by her father. We can call it one of the 'arguments' of the verb ask.
*She asked about Janice was abused by her father.
This is ungrammatical. The preposition about, like all other prepositions, must be followed by an argument, not a sentence. We can correct it by transforming the finite verb was into a gerund:
She asked about Janice being abused by her father.