Both are correct, but you probably mean 1. 1. = She is somewhat introverted. 2. = She is a small person who is an introvert. If you want to use it as an adjective, the word is INTROVERTED. So you could also say, She is a little (bit) introverted, which would mean the same as 1.

The problem with #2 is that it tries to use "little" as an adverb. However, "little" cannot be an adverb. It is an adjective. You could rescue the sentence by using an adverb that means something similar: She is slightly an introvert. She is rather an introvert. She is somewhat an introvert. She is to a certain extent an introvert. She is sort of an introvert. "A bit of" functions as an adverb, similar to "to a certain extent".

Both sentences are correct! But if the idea you are trying to say is that the person you are describing has that little introverted type of personality, then sentence 1 is a more fitting sentence and sentence number 2 is better constructed as "She's a little introverted." Hope this helps! 🌟