If you want to convey the meaning of a very firm hold on the fork, your first two choices are fine and don't necessarily connote taking into one's hand before holding (as Tim Romano pointed out in his comment). I would say that clutch has a slightly more "not implying taking first" feel than grip:
clutch (LDOCE):
clutch
1 [transitive]
to hold something tightly because you do not want to lose it
MW:
to hold onto (someone or something) tightly with your hand
There are other definitions in these dictionaries, where to clutch also includes taking hold of, but the fact that there is a definition without this meaning says (to me at least) that the word can be used without this "to take first" connotation. Same goes for:
to grip (LDOCE):
[transitive]
to hold something very tightly:
I haven't found evidence that same applies to grasp.
If you don't want to say that the hold was firm, then a present participle form of your very own to hold would work:
"I'm not in the mood for jokes," she said, (still) holding her fork and looking at her plate again.
Or if you would allow slight rephrasing:
"I'm not in the mood for jokes," she said, looking at her plate again while holding her fork.
"I'm not in the mood for jokes," she said, with a fork in her hand, looking at her plate again.