S.H.
Does she nap? I mean, having a daily good solid nap? Regularly?
If not, then she is over-tired. And over-tired babies do not fare well, they get MEGA fussy and lose tolerance and are not pleasant.
They have no control, over their emotions at this age. Emotions are not even fully developed yet at this age.
Is she hungry?
My daughter, since a baby, gets real irritable if hungry. I do too.
And, maybe she is the type that just likes "routine". Some babies/kids are this way. And if not, they do not transition well to anything, get cranky/tantrum and just go bonkers. Because they like routine. And regularity. Not just happenstance things going on.
Also something note worthy: my friend had a baby like that. ALWAYS crying and fussy. Never happy. She took her baby to the Doctor, the Doctor looked the baby over real carefully from head to toe. It was found... that a blond hair was wrapped around her baby's toe. Getting tighter and into the skin. Causing pain of course. The hair was blond and so it was totally invisible and hard to detect to a normal person. Once the Doctor removed the tangled hair. Her baby, was HAPPY again. And normal. And fine. The hair was so tangled on the toe that the Doctor had to very carefully snip it off. It would not come off by just tugging it with your fingers.
all the best,
Susan