S.H.
Teach her, other ways of coping. Coping skills, are not inherent or instinctual in kids. It is learned. Not even some adults have that 'skill' or ability.
Often also, if you initially validate a kids feelings... then, segue into guiding them onto 'how' to problem solve it... that will help.
But if you immediately tell a kid why they shouldn't feel that way.... or try to convince them why they shouldn't be feeling that way, it makes things worse.
The book "How To Talk So Kids Will Listen, and Listen So Kids Will Talk" is good.
Even to use with adults.
Also, it may help to keep in mind, that a kid this age, they do NOT have full developed emotions.... much less the understanding of EVERY little emotion they have... nor can they explain it or articulate it. Thus, they cry or tantrum. A young child's repertoire, of skills... is not fully mastered yet. For coping with problems or frustrations. They don't even have fully developed "deductive reasoning" yet either. Their brain development is still developing and their spectrum of emotions. They are not articulate about it yet, nor even about social skills.
Also, if a kid does not nap or is tired/over-tired... they get like this.
Also, if she is like my daughter... my daughter HAS to graze... throughout the day, or she gets Hypoglycemic... low blood sugar. When ANYONE has that, or they are hungry, it affects the physiological functioning of a person. Hence, they get irritable and moody and have nil, patience. So with my daughter, she has to snack throughout the day. If the blood sugar levels plummet... or she has gone too long without something in her, she can really get, fussy. But I know my daughter... thus, I can read her like a book and know, when she must have a snack. We only have healthy stuff, so whatever she eats and no matter how often she eats, it is not a big deal. She eats, when/if her body needs it. I taught her to recognize, her body's cues.