Is the sentence
"She very wants to do it."
could be correct in a meaning of:
She wants to do it very much.
I mean to ask if it is a grammatical sentence at all.
No, “very” is a qualifier that is used to add more detail to a noun or adjective’s meaning (for example “she was very happy”) and so can’t come before a verb.
In the example “She very wants to do it” the word “really” would be correct, changing the sentence to “She really wants to do it”. “Really” has a very similar meaning in this context and can be used to enhance a verb.