Could it be trapped wind? If you try some tummy massage (you’ll probably find instructions on YouTube) she might initially cry more and then settle - my boy always calms after that but it initially prompts a big scream as it’s uncomfortable when the wind moves around his tum
No it's probably just a developmental leap, mine is exactly like this as well. It's so tiring. He's been like this on & off for about 3 weeks. It's almost like he's bored/wants attention/isn't happy but doesn't know why. Things I've found help is keeping busy with him, getting outside, using a carrier to carry him round doing jobs with me, singing and dancing for him trying to entertain him. But also accepting it's just a phase and it will pass - I've looked on Mumsnet/Reddit and loads of people say it's really common to have a fussy 4/5 month old xx
If it’s teething then try the teething gel or powder, or try rub her gums with a clean finger and see if she settles