I think instead of "had" you should use "got"
She - Subject
suddenly got - verb phrase (the main verb is always the last verb so it is "got" and you can consider "suddenly" as an adverb of manner/time (i am not sure if it's manner or time since it describes the two.)
cramps.- direct object (Since it answer the question (verb + what?. Like "she suddenly got what? cramps.)
Sorry not so sure though,but this is what i think.