彼女がどんなに喜んでいるのかわからなかった。

she; her; her; girlfriend; sweetheart

indicates sentence subject (occasionally object); indicates possessive (esp. in literary expressions); but; however; still; and

how; how much

to be delighted; to be glad; to be pleased; to congratulate; to gratefully accept

indicates possessive; nominalizes verbs and adjectives; substitutes for "ga" in subordinate phrases; (at sentence-end, falling tone) indicates a confident conclusion; (at sentence-end) indicates emotional emphasis; (at sentence-end, rising tone) indicates question

indicates a question (sometimes rhetorical); or; whether or not; some- (e.g. something, someone); indicates doubt, uncertainty, etc.; emphatic prefix; suffix forming adjectives or adverbs; in that way

to understand; to comprehend; to grasp; to see; to get; to follow; to become clear; to be known; to be discovered; to be realized; to be realised; to be found out