Hey & welcome.

William gave you great advice.  Mostly you want to look for something on the product or package that reads 'authentic' or 'complete score'.  There are simplified versions which just show chord symbols, lyrics & melody.  You want something that shows the complete guitar notation & tab.

Musicnotes is a great site for notation.  But even there you need to make sure you are buying what you want.  For example, this is one of the options when you search for The Beatles 'She Loves You'.

https://www.musicnotes.com/sheetmusic/mtd.asp?ppn=MN0101933

But you want the complete scores, then you're looking for this Hal Leonard book.

https://www.halleonard.com/product-family/PC9796/the-beatles-complete-scores

In my experience Hal Leonard is one of the better companies.  But it depends on what style of music, artist or even song you are looking for.  And sometimes even if it claims to be 'authentic' or 'complete' there is the chance it will contain substitutions or errors.  

What exactly are you looking for?

Hope that helps!