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:
to hold something tightly because you do not want to lose it
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):
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.