Anxiety in Toddlers

I've read that all children in one way or another suffer through anxiety as their imagination and curiosity begin to expand, but my 3 yr old (almost 4) daughter is super terrified of everything. When I try to understand some things that she is particularly scared of, it's difficult to translate. Her speech is not that great, she knows a variety of words but she doesn't seem confident in pronouncing them clearly or correctly. She will scream bloody murder if a butterfly is near her. We recently adopted a kitten in hopes that she would really enjoy her own pet, but she crys and runs up the stairs if it even appears to be stepping her way. We've learned that her room must be fully lit for her to fall asleep. Any and all night lights do not illuminate it enough for her. My daughter is extremely sweet but extremely timid and I'm just curious if this is just her natural sensitive way, or are her fears too extreme for her age?