The phonetic spelling of “she” is written as shee, but how can its weak sound form be written?

Question

Answer

I think you are overthinking this.

I am a native speaker and I usually only pronounce "she" like "sheeeeeeeeeeeeeeeeee",
unless it is part of a contraction like "she'll"

For example: 
"She'll be arriving shortly."

Good luck!

Answer

I'm a native US speaker and I only know one pronunciation of "she."

I tried saying sentences with the word "she" as fast as I could, and in as relaxed a way as I could, and I still pronounced it "shee."

To confirm this, I checked an American dictionary, and noticed that as I expected, there are two pronunciations for "the," but only one for "she."

I believe there is only one pronunciation of the word "she."

Answer

two sounds, sh and i (ee)

Answer

I agree with Ian.  What do you mean by weak form?  I'm not aware of any other forms of 'she'.